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<TITLE>14. CIS, TDHF, and TDDFT</TITLE>
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<B> Next:</B> <A NAME="tex2html1244"
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HREF="node17.html">15. Tensor Contraction Engine</A>
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<B> Previous:</B> <A NAME="tex2html1234"
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HREF="node15.html">13. COSMO</A>
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  <B> <A NAME="tex2html1242"
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HREF="node2.html">Contents</A></B>
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<BR>
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<BR>
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<!--Table of Child-Links-->
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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
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<UL>
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<LI><A NAME="tex2html1245"
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HREF="node16.html#SECTION001610000000000000000">14.1 Overview</A>
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<LI><A NAME="tex2html1246"
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HREF="node16.html#SECTION001620000000000000000">14.2 Performance of CIS, TDHF, and TDDFT methods</A>
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<LI><A NAME="tex2html1247"
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HREF="node16.html#SECTION001630000000000000000">14.3 Input syntax</A>
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<LI><A NAME="tex2html1248"
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HREF="node16.html#SECTION001640000000000000000">14.4 Keywords of <TT>TDDFT</TT> input block</A>
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<UL>
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<LI><A NAME="tex2html1249"
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HREF="node16.html#SECTION001641000000000000000">14.4.1 <TT>CIS</TT> and <TT>RPA</TT> -- the Tamm-Dancoff approximation</A>
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<LI><A NAME="tex2html1250"
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HREF="node16.html#SECTION001642000000000000000">14.4.2 <TT>NROOTS</TT> -- the number of excited states</A>
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<LI><A NAME="tex2html1251"
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HREF="node16.html#SECTION001643000000000000000">14.4.3 <TT>MAXVECS</TT> -- the subspace size</A>
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<LI><A NAME="tex2html1252"
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HREF="node16.html#SECTION001644000000000000000">14.4.4 <TT>SINGLET</TT> and <TT>NOSINGLET</TT> -- singlet excited states</A>
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<LI><A NAME="tex2html1253"
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HREF="node16.html#SECTION001645000000000000000">14.4.5 <TT>TRIPLET</TT> and <TT>NOTRIPLET</TT> -- triplet excited states</A>
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<LI><A NAME="tex2html1254"
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HREF="node16.html#SECTION001646000000000000000">14.4.6 <TT>THRESH</TT> -- the convergence threshold of Davidson iteration</A>
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<LI><A NAME="tex2html1255"
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HREF="node16.html#SECTION001647000000000000000">14.4.7 <TT>MAXITER</TT> -- the maximum number of Davidson iteration</A>
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<LI><A NAME="tex2html1256"
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HREF="node16.html#SECTION001648000000000000000">14.4.8 <TT>TARGET</TT> and <TT>TARGETSYM</TT>-- the target root and its symmetry</A>
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<LI><A NAME="tex2html1257"
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HREF="node16.html#SECTION001649000000000000000">14.4.9 <TT>SYMMETRY</TT> -- restricting the excited state symmetry</A>
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<LI><A NAME="tex2html1258"
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HREF="node16.html#SECTION0016410000000000000000">14.4.10 <TT>ALGORITHM</TT> -- algorithms for tensor contractions</A>
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<LI><A NAME="tex2html1259"
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HREF="node16.html#SECTION0016411000000000000000">14.4.11 <TT>FREEZE</TT> -- the frozen core/virtual approximation</A>
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<LI><A NAME="tex2html1260"
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HREF="node16.html#SECTION0016412000000000000000">14.4.12 <TT>PRINT</TT> -- the verbosity</A>
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</UL>
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<BR>
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<LI><A NAME="tex2html1261"
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HREF="node16.html#SECTION001650000000000000000">14.5 Sample input</A>
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</UL>
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<!--End of Table of Child-Links-->
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<HR>
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<H1><A NAME="SECTION001600000000000000000">
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14. CIS, TDHF, and TDDFT</A>
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</H1>
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<A NAME="sec:tddft"></A>
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<P>
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<H1><A NAME="SECTION001610000000000000000">
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14.1 Overview</A>
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</H1>
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<P>
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NWChem supports a spectrum of single excitation theories for
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vertical excitation energy calculations, namely, configuration interaction
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singles (CIS),<A NAME="tex2html42"
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HREF="footnode.html#foot4507"><SUP>14.1</SUP></A>
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time-dependent Hartree-Fock (TDHF or also known as
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random-phase approximation RPA), time-dependent density functional
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theory (TDDFT),<A NAME="tex2html43"
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HREF="footnode.html#foot4508"><SUP>14.2</SUP></A>
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and Tamm-Dancoff approximation to TDDFT.<A NAME="tex2html44"
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HREF="footnode.html#foot4509"><SUP>14.3</SUP></A>These methods
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are implemented in a single framework that invokes Davidson's trial vector
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algorithm (or its modification for a non-Hermitian eigenvalue problem).<A NAME="tex2html45"
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HREF="footnode.html#foot4510"><SUP>14.4</SUP></A>The capabilities of the module are summarized as follows:
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<UL>
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<LI>Vertical excitation energies,
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</LI>
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<LI>Spin-restricted singlet and triplet excited states for closed-shell systems,
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</LI>
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<LI>Spin-unrestricted doublet, etc., excited states for open-shell systems,
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</LI>
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<LI>Tamm-Dancoff and full time-dependent linear response theories,
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</LI>
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<LI>Davidson's trial vector algorithm,
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</LI>
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<LI>Symmetry (irreducible representation) characterization and specification,
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</LI>
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<LI>Spin multiplicity characterization and specification,
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</LI>
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<LI>Transition moments and oscillator strengths,
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</LI>
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<LI>Geometrical first and second derivatives of vertical excitation energies
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by numerical differentiation,
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</LI>
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<LI>Disk-based and fully incore algorithms,
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</LI>
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<LI>Multiple and single trial-vector processing algorithms,
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</LI>
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<LI>Frozen core and virtual approximation.
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</LI>
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</UL>
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<P>
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New capability added in the latest version (4.6) is:
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<UL>
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<LI>Asymptotically correct exchange-correlation potential by van Leeuwen and Baerends,<A NAME="tex2html46"
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HREF="footnode.html#foot4511"><SUP>14.5</SUP></A>
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</LI>
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<LI>Asymptotic correction by Casida and Salahub,<A NAME="tex2html47"
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HREF="footnode.html#foot4512"><SUP>14.6</SUP></A>
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</LI>
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<LI>Asymptotic correction by Hirata, Zhan, Aprà, Windus, and Dixon.<A NAME="tex2html48"
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HREF="footnode.html#foot4513"><SUP>14.7</SUP></A>
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</LI>
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</UL>
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These are very effective way to rectify the shortcomings of TDDFT when applied to Rydberg excited states (see below).
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<P>
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<H1><A NAME="SECTION001620000000000000000">
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14.2 Performance of CIS, TDHF, and TDDFT methods</A>
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</H1>
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<P>
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The accuracy of CIS and TDHF for excitation energies of closed-shell systems
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are comparable to each other, and are normally considered a zeroth-order
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description of the excitation process. These methods are particularly well balanced
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in describing Rydberg excited states, in contrast to TDDFT.
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However, for open-shell systems,
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the errors in the CIS and TDHF excitation energies are often excessive, primarily
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due to the multi-determinantal character of the ground and excited state wave functions
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of open-shell systems in a HF reference.<A NAME="tex2html49"
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HREF="footnode.html#foot4514"><SUP>14.8</SUP></A>
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The scaling of the computational cost of a CIS
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or TDHF calculation per state with respect to the system size is the same as that for
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a HF calculation for the ground state, since the critical step of the both methods are
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the Fock build, namely, the contraction of two-electron integrals with density matrices.
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It is usually necessary to include two sets of diffuse exponents in the basis set
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to properly account for the diffuse Rydberg excited states of neutral species.
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<P>
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The accuracy of TDDFT may vary depending on the exchange-correlation functional.
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In general, the exchange-correlation functionals that are widely used today and are implemented
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in NWChem work well for low-lying valence excited states. However, for high-lying diffuse
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excited states and Rydberg excited states in particular, TDDFT employing these
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conventional functionals breaks down and the excitation energies are substantially
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underestimated. This is because of the fact that the exchange-correlation potentials
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generated from these functionals decay too rapidly (exponentially) as opposed to the
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slow <IMG
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WIDTH="40" HEIGHT="31" ALIGN="MIDDLE" BORDER="0"
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SRC="img111.gif"
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ALT="$-1/r$"> asymptotic decay of the true potential. A rough but useful index is the
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negative of the highest occupied KS orbital energy; when the calculated excitation energies
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become close to this threshold, these numbers are most likely underestimated relative
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to experimental results.<A NAME="tex2html50"
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HREF="footnode.html#foot4515"><SUP>14.9</SUP></A> It appears that TDDFT provides a better-balanced description
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of radical excited states.<A NAME="tex2html51"
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HREF="footnode.html#foot4516"><SUP>14.10</SUP></A>
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This may be traced to the fact that, in DFT, the ground state
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wave function is represented well as a single KS determinant, with less multi-determinantal
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character and less spin contamination, and hence the excitation thereof is described well
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as a simple one electron transition. The computational cost per state of TDDFT calculations
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scales as the same as the ground state DFT calculations, although the prefactor of the scaling
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may be much greater in the former.
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<P>
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A very simple and effecive way to rectify the TDDFT's failure for Rydberg excited states
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has been proposed by Tozer and Handy<A NAME="tex2html52"
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HREF="footnode.html#foot4517"><SUP>14.11</SUP></A> and by Casida and Salahub (see previous reference). They proposed to splice a <IMG
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WIDTH="40" HEIGHT="31" ALIGN="MIDDLE" BORDER="0"
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SRC="img111.gif"
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ALT="$-1/r$"> asymptotic
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tail to an exchange-correlation potential that does not have the correct asymptotic behavior.
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Because the approximate exchange-correlation potentials are too shallow everywhere, a negative constant
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must be added to them before they can be spliced to the <IMG
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WIDTH="40" HEIGHT="31" ALIGN="MIDDLE" BORDER="0"
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SRC="img111.gif"
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ALT="$-1/r$"> tail seamlessly in a region that is not
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sensitive to chemical effects or to the long-range behavior. The negative constant or the shift is usually
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taken to be the difference of the HOMO energy from the true ionization potential, which can be obtained
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either from experiment or from a <IMG
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WIDTH="17" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
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SRC="img104.gif"
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ALT="$\Delta$">SCF calculation. Recently, we proposed a new, expedient, and
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self-contained asymptotic correction that does not require an ionization potential (or shift) as an external parameter from a separate calculation.<A NAME="tex2html53"
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HREF="footnode.html#foot4518"><SUP>14.12</SUP></A> In this scheme, the shift is computed by a semi-empirical
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formula proposed by Zhan, Nichols, and Dixon.<A NAME="tex2html54"
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HREF="footnode.html#foot4519"><SUP>14.13</SUP></A> Both Casida-Salahub scheme and this new asymptotic correction scheme give considerably improved (Koopmans type) ionization potentials and Rydberg excitation energies.
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The latter, however, supply the shift by itself unlike to former.
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<P>
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<H1><A NAME="SECTION001630000000000000000">
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14.3 Input syntax</A>
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</H1>
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<P>
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The module is called TDDFT as TDDFT employing a hybrid HF-DFT functional
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encompasses all of the above-mentioned methods implemented. To use this
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module, one needs to specify <code>TDDFT</code> on the task directive, e.g.,
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<PRE>
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TASK TDDFT ENERGY
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</PRE>
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for a single-point excitation energy calculation, and
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<PRE>
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TASK TDDFT OPTIMIZE
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</PRE>
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for an excited-state geometry optimization (and perhaps an adiabatic
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excitation energy calculation), and
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<PRE>
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TASK TDDFT FREQUENCIES
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</PRE>
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for an excited-state vibrational frequency calculation. The TDDFT module
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first invokes DFT module for a ground-state calculation (regardless of
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whether the calculations uses a HF reference as in CIS or TDHF or a DFT
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functional), and hence there is no need to perform a separate ground-state
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DFT calculation prior to calling a TDDFT task. When no second argument
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of the task directive is given, a single-point excitation energy calculation
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will be assumed. For geometry optimizations, it is usually necessary to
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specify the target excited state and its irreducible representation it
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belongs to. See the subsections <code>TARGET</code> and <code>TARGETSYM</code> for
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more detail.
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<P>
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Individual parameters and keywords may be supplied in the TDDFT input
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block. The syntax is:
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<PRE>
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TDDFT
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[(CIS||RPA) default RPA]
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[NROOTS <integer nroots default 1>]
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[MAXVECS <integer maxvecs default 1000>]
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[(SINGLET||NOSINGLET) default SINGLET]
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[(TRIPLET||NOTRIPLET) default TRIPLET]
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[THRESH <double thresh default 1e-4>]
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[MAXITER <integer maxiter default 100>]
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[TARGET <integer target default 1>]
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[TARGETSYM <character targetsym default 'none'>]
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[SYMMETRY]
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[ALGORITHM <integer algorithm default 0>]
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[FREEZE [[core] (atomic || <integer nfzc default 0>)] \
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[virtual <integer nfzv default 0>]]
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[PRINT (none||low||medium||high||debug)
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<string list_of_names ...>]
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END
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</PRE>
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<P>
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The user can also specify the reference wave function in the DFT input block
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(even when CIS and TDHF calculations are requested). See the section of Sample
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input and output for more details.
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<P>
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Since each keyword has a default value, a minimal input file will be
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<PRE>
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GEOMETRY
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Be 0.0 0.0 0.0
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END
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BASIS
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Be library 6-31G**
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END
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TASK TDDFT ENERGY
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</PRE>
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<P>
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Note that the keyword for the asymptotic correction must be given in the
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DFT input block, since all the effects of the correction (and also changes in the
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computer program) occur in the SCF calculation stage. See Chapter 11 (keyword <code>CS00</code> and
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<code>LB94</code>) for details.
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<P>
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<H1><A NAME="SECTION001640000000000000000">
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14.4 Keywords of <TT>TDDFT</TT> input block</A>
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</H1>
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<P>
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<H2><A NAME="SECTION001641000000000000000">
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14.4.1 <TT>CIS</TT> and <TT>RPA</TT> -- the Tamm-Dancoff approximation</A>
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</H2>
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<P>
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These keywords toggle the Tamm-Dancoff approximation. <code>CIS</code> means
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that the Tamm-Dancoff approximation is used and the CIS or Tamm-Dancoff TDDFT
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calculation is requested. <code>RPA</code>, which is the default, requests
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TDHF (RPA) or TDDFT calculation.
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<P>
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The performance of CIS (Tamm-Dancoff TDDFT) and RPA (TDDFT) are comparable in
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accuracy. However, the computational cost is slightly greater in the latter due to
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the fact that the latter involves a non-Hermitian eigenvalue problem and requires
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left and right eigenvectors while the former needs just one set of eigenvectors of
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a Hermitian eigenvalue problem. The latter has much greater chance of
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aborting the calculation due to triplet near instability or other instability
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problems.
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<P>
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<H2><A NAME="SECTION001642000000000000000">
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14.4.2 <TT>NROOTS</TT> -- the number of excited states</A>
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</H2>
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<P>
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One can specify the number of excited state roots to be determined. The default
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value is <code>1</code>. It is advised that the users request several more roots than actually
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needed, since owing to the nature of the trial vector algorithm, some low-lying
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roots can be missed when they do not have sufficient overlap with the initial guess
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vectors.
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<P>
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<H2><A NAME="SECTION001643000000000000000">
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14.4.3 <TT>MAXVECS</TT> -- the subspace size</A>
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</H2>
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<P>
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This keyword limits the subspace size of Davidson's algorithm; in other words, it
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is the maximum number of trial vectors that the calculation is allowed to hold.
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Typically, 10 to 20 trial vectors are needed for each excited state root to be
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converged. However, it need not exceed the product of the number of occupied
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orbitals and the number of virtual orbitals. The default value is <code>1000</code>.
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<P>
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<H2><A NAME="SECTION001644000000000000000">
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14.4.4 <TT>SINGLET</TT> and <TT>NOSINGLET</TT> -- singlet excited states</A>
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</H2>
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<P>
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<code>SINGLET</code> (<code>NOSINGLET</code>) requests (suppresses) the calculation of singlet
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excited states when the reference wave function is closed shell. The default
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is <code>SINGLET</code>.
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<P>
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<H2><A NAME="SECTION001645000000000000000">
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14.4.5 <TT>TRIPLET</TT> and <TT>NOTRIPLET</TT> -- triplet excited states</A>
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</H2>
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<P>
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<code>TRIPLET</code> (<code>NOTRIPLET</code>) requests (suppresses) the calculation of triplet
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excited states when the reference wave function is closed shell. The default
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is <code>TRIPLET</code>.
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<P>
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<H2><A NAME="SECTION001646000000000000000">
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14.4.6 <TT>THRESH</TT> -- the convergence threshold of Davidson iteration</A>
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</H2>
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<P>
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This keyword specifies the convergence threshold of Davidson's iterative algorithm
|
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to solve a matrix eigenvalue problem. The threshold refers to the norm of residual,
|
|
namely, the difference between the left-hand side and right-hand side of the matrix
|
|
eigenvalue equation with the current solution vector. With the default value of
|
|
<code>1e-4</code>, the excitation energies are usually converged to <code>1e-5</code> hartree.
|
|
|
|
<P>
|
|
|
|
<H2><A NAME="SECTION001647000000000000000">
|
|
14.4.7 <TT>MAXITER</TT> -- the maximum number of Davidson iteration</A>
|
|
</H2>
|
|
|
|
<P>
|
|
It typically takes 10-30 iterations for the Davidson algorithm to get converged results.
|
|
The default value is <code>100</code>.
|
|
|
|
<P>
|
|
|
|
<H2><A NAME="SECTION001648000000000000000">
|
|
14.4.8 <TT>TARGET</TT> and <TT>TARGETSYM</TT>-- the target root and its symmetry</A>
|
|
</H2>
|
|
|
|
<P>
|
|
At the moment, the first and second geometrical derivatives of excitation
|
|
energies that are needed in force, geometry, and frequency calculations are
|
|
obtained by numerical differentiation. These keywords may be used to specify
|
|
which excited state root is being used for the geometrical derivative calculation.
|
|
For instance, when <code>TARGET 3</code> and <code>TARGETSYM a1g</code> are included in the
|
|
input block, the total energy (ground state energy plus excitation energy)
|
|
of the third lowest excited state root (excluding the ground state) transforming as
|
|
the irreducible representation <code>a1g</code> will be passed to the module which performs
|
|
the derivative calculations. The default values of these keywords are <code>1</code> and <code>none</code>,
|
|
respectively.
|
|
|
|
<P>
|
|
The keyword <code>TARGETSYM</code> is essential in excited state geometry
|
|
optimization, since it is very common that the order of excited states changes due to
|
|
the geometry changes in the course of optimization. Without specifying the <code>TARGETSYM</code>,
|
|
the optimizer could (and would likely) be optimizing the geometry of an excited state that
|
|
is different from the one the user had intended to optimize at the starting geometry.
|
|
On the other hand, in the frequency calculations, <code>TARGETSYM</code> must be <code>none</code>,
|
|
since the finite displacements given in the course of frequency calculations will lift
|
|
the spatial symmetry of the equilibrium geometry. When these finite displacements can
|
|
alter the order of excited states including the target state, the frequency calculation
|
|
is not be feasible.
|
|
|
|
<P>
|
|
|
|
<H2><A NAME="SECTION001649000000000000000">
|
|
14.4.9 <TT>SYMMETRY</TT> -- restricting the excited state symmetry</A>
|
|
</H2>
|
|
|
|
<P>
|
|
By adding this keyword to the input block, the user can request the module to
|
|
generate the initial guess vectors transforming as the
|
|
same irreducible representation as <code>TARGETSYM</code>. This causes the final
|
|
excited state roots be (exclusively) dominated by those with the specified
|
|
irreducible representation. This may be useful, when the user is interested in
|
|
just the optically allowed transitions, or in the geometry optimization of
|
|
an excited state root with a particular irreducible representation. By default,
|
|
this option is not set. <code>TARGETSYM</code> must be specified when <code>SYMMETRY</code>
|
|
is invoked.
|
|
|
|
<P>
|
|
|
|
<H2><A NAME="SECTION0016410000000000000000">
|
|
14.4.10 <TT>ALGORITHM</TT> -- algorithms for tensor contractions</A>
|
|
</H2>
|
|
|
|
<P>
|
|
There are four distinct algorithms to choose from, and the default value
|
|
of <code>0</code> (optimal) means that the program makes an optimal choice from the four
|
|
algorithms on the basis of available memory. In the order of decreasing memory requirement,
|
|
the four algorithms are:
|
|
|
|
<UL>
|
|
<LI><code>ALGORITHM 1</code> : Incore, multiple tensor contraction,
|
|
</LI>
|
|
<LI><code>ALGORITHM 2</code> : Incore, single tensor contraction,
|
|
</LI>
|
|
<LI><code>ALGORITHM 3</code> : Disk-based, multiple tensor contraction,
|
|
</LI>
|
|
<LI><code>ALGORITHM 4</code> : Disk-based, single tensor contraction.
|
|
</LI>
|
|
</UL>
|
|
The incore algorithm stores all the trial and product vectors in memory across
|
|
different nodes with the GA,
|
|
and often decreases the <code>MAXITER</code> value to accommodate them. The disk-based
|
|
algorithm stores the vectors on disks across different nodes with the DRA, and
|
|
retrieves each vector one at a time when it is needed. The multiple and single
|
|
tensor contraction refers to whether just one or more than one trial vectors
|
|
are contracted with integrals. The multiple tensor contraction algorithm is
|
|
particularly effective (in terms of speed) for CIS and TDHF, since the number of
|
|
the direct evaluations of two-electron integrals is diminished substantially.
|
|
|
|
<P>
|
|
|
|
<H2><A NAME="SECTION0016411000000000000000">
|
|
14.4.11 <TT>FREEZE</TT> -- the frozen core/virtual approximation</A>
|
|
</H2>
|
|
|
|
<P>
|
|
Some of the lowest-lying core orbitals and/or some of the highest-lying
|
|
virtual orbitals may be excluded in the CIS, TDHF, and TDDFT calculations
|
|
by this keyword (this does not affect the ground state HF or DFT calculation).
|
|
No orbitals are frozen by default. To exclude the atom-like
|
|
core regions altogether, one may request
|
|
<PRE>
|
|
FREEZE atomic
|
|
</PRE>
|
|
To specify the number of lowest-lying occupied orbitals be excluded, one may use
|
|
<PRE>
|
|
FREEZE 10
|
|
</PRE>
|
|
which causes 10 lowest-lying occupied orbitals excluded.
|
|
This is equivalent to writing
|
|
<PRE>
|
|
FREEZE core 10
|
|
</PRE>
|
|
To freeze the highest virtual orbitals, use the <code>virtual</code>
|
|
keyword. For instance, to freeze the top 5 virtuals
|
|
<PRE>
|
|
FREEZE virtual 5
|
|
</PRE>
|
|
|
|
<P>
|
|
|
|
<H2><A NAME="SECTION0016412000000000000000">
|
|
14.4.12 <TT>PRINT</TT> -- the verbosity</A>
|
|
</H2>
|
|
|
|
<P>
|
|
This keyword changes the level of output verbosity. One may also
|
|
request some particular items in Table <A HREF="node16.html#tbl:tddft-printable">14.1</A> printed.
|
|
|
|
<P>
|
|
<BR>
|
|
<DIV ALIGN="CENTER">
|
|
<A NAME="tbl:tddft-printable"></A><A NAME="4488"></A>
|
|
<TABLE CELLPADDING=3 BORDER="1" ALIGN="CENTER">
|
|
<CAPTION><STRONG>Table 14.1:</STRONG>
|
|
Printable items in the TDDFT modules and their default print levels.</CAPTION>
|
|
<TR><TD ALIGN="LEFT">Item</TD>
|
|
<TD ALIGN="LEFT">Print Level</TD>
|
|
<TD ALIGN="LEFT">Description</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``timings''</TD>
|
|
<TD ALIGN="LEFT">high</TD>
|
|
<TD ALIGN="LEFT">CPU and wall times spent in each step</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``trial vectors''</TD>
|
|
<TD ALIGN="LEFT">high</TD>
|
|
<TD ALIGN="LEFT">Trial CI vectors</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``initial guess''</TD>
|
|
<TD ALIGN="LEFT">debug</TD>
|
|
<TD ALIGN="LEFT">Initial guess CI vectors</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``general information''</TD>
|
|
<TD ALIGN="LEFT">default</TD>
|
|
<TD ALIGN="LEFT">General information</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``xc information''</TD>
|
|
<TD ALIGN="LEFT">default</TD>
|
|
<TD ALIGN="LEFT">HF/DFT information</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``memory information''</TD>
|
|
<TD ALIGN="LEFT">default</TD>
|
|
<TD ALIGN="LEFT">Memory information</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``convergence''</TD>
|
|
<TD ALIGN="LEFT">debug</TD>
|
|
<TD ALIGN="LEFT">Convergence</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``subspace''</TD>
|
|
<TD ALIGN="LEFT">debug</TD>
|
|
<TD ALIGN="LEFT">Subspace representation of CI matrices</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``transform''</TD>
|
|
<TD ALIGN="LEFT">debug</TD>
|
|
<TD ALIGN="LEFT">MO to AO and AO to MO transformation of CI vectors</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``diagonalization''</TD>
|
|
<TD ALIGN="LEFT">debug</TD>
|
|
<TD ALIGN="LEFT">Diagonalization of CI matrices</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``iteration''</TD>
|
|
<TD ALIGN="LEFT">default</TD>
|
|
<TD ALIGN="LEFT">Davidson iteration update</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``contract''</TD>
|
|
<TD ALIGN="LEFT">debug</TD>
|
|
<TD ALIGN="LEFT">Integral transition density contraction</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``ground state''</TD>
|
|
<TD ALIGN="LEFT">default</TD>
|
|
<TD ALIGN="LEFT">Final result for ground state</TD>
|
|
</TR>
|
|
<TR><TD ALIGN="LEFT">``excited state''</TD>
|
|
<TD ALIGN="LEFT">low</TD>
|
|
<TD ALIGN="LEFT">Final result for target excited state</TD>
|
|
</TR>
|
|
</TABLE>
|
|
</DIV>
|
|
<BR>
|
|
|
|
<P>
|
|
|
|
<H1><A NAME="SECTION001650000000000000000">
|
|
14.5 Sample input</A>
|
|
</H1>
|
|
|
|
<P>
|
|
The following is a sample input for a spin-restricted TDDFT calculation of
|
|
singlet excitation energies for the water molecule at the B3LYP/6-31G*.
|
|
<PRE>
|
|
START h2o
|
|
|
|
TITLE "B3LYP/6-31G* H2O"
|
|
|
|
GEOMETRY
|
|
O 0.00000000 0.00000000 0.12982363
|
|
H 0.75933475 0.00000000 -0.46621158
|
|
H -0.75933475 0.00000000 -0.46621158
|
|
END
|
|
|
|
BASIS
|
|
* library 6-31G*
|
|
END
|
|
|
|
DFT
|
|
XC B3LYP
|
|
END
|
|
|
|
TDDFT
|
|
RPA
|
|
NROOTS 20
|
|
END
|
|
|
|
TASK TDDFT ENERGY
|
|
</PRE>
|
|
|
|
<P>
|
|
To perform a spin-unrestricted TDHF/aug-cc-pVDZ calculation for the CO+ radical,
|
|
<PRE>
|
|
START co
|
|
|
|
TITLE "TDHF/aug-cc-pVDZ CO+"
|
|
|
|
CHARGE 1
|
|
|
|
GEOMETRY
|
|
C 0.0 0.0 0.0
|
|
O 1.5 0.0 0.0
|
|
END
|
|
|
|
BASIS
|
|
* library aug-cc-pVDZ
|
|
END
|
|
|
|
DFT
|
|
XC HFexch
|
|
MULT 2
|
|
END
|
|
|
|
TDDFT
|
|
RPA
|
|
NROOTS 5
|
|
END
|
|
|
|
TASK TDDFT ENERGY
|
|
</PRE>
|
|
|
|
<P>
|
|
A geometry optimization followed by a frequency calculation for an excited state
|
|
is carried out for BF at the CIS/6-31G* level in the following sample input.
|
|
<PRE>
|
|
START bf
|
|
|
|
TITLE "CIS/6-31G* BF optimization frequencies"
|
|
|
|
GEOMETRY
|
|
B 0.0 0.0 0.0
|
|
F 0.0 0.0 1.2
|
|
END
|
|
|
|
BASIS
|
|
* library 6-31G*
|
|
END
|
|
|
|
DFT
|
|
XC HFexch
|
|
END
|
|
|
|
TDDFT
|
|
CIS
|
|
NROOTS 3
|
|
NOTRIPLET
|
|
TARGET 1
|
|
END
|
|
|
|
TASK TDDFT OPTIMIZE
|
|
|
|
TASK TDDFT FREQUENCIES
|
|
</PRE>
|
|
|
|
<P>
|
|
TDDFT with an asymptotically corrected SVWN exchange-correlation potential.
|
|
Casida-Salahub scheme has been used with the shift value of 0.1837 a.u. supplied
|
|
as an input parameter.
|
|
<PRE>
|
|
START tddft_ac_co
|
|
|
|
GEOMETRY
|
|
O 0.0 0.0 0.0000
|
|
C 0.0 0.0 1.1283
|
|
END
|
|
|
|
BASIS SPHERICAL
|
|
C library aug-cc-pVDZ
|
|
O library aug-cc-pVDZ
|
|
END
|
|
|
|
DFT
|
|
XC Slater VWN_5
|
|
CS00 0.1837
|
|
END
|
|
|
|
TDDFT
|
|
NROOTS 12
|
|
END
|
|
|
|
TASK TDDFT ENERGY
|
|
</PRE>
|
|
|
|
<P>
|
|
TDDFT with an asymptotically corrected B3LYP exchange-correlation potential.
|
|
Hirata-Zhan-Apra-Windus-Dixon scheme has been used (this is only meaningful
|
|
with B3LYP functional).
|
|
<PRE>
|
|
START tddft_ac_co
|
|
|
|
GEOMETRY
|
|
O 0.0 0.0 0.0000
|
|
C 0.0 0.0 1.1283
|
|
END
|
|
|
|
BASIS SPHERICAL
|
|
C library aug-cc-pVDZ
|
|
O library aug-cc-pVDZ
|
|
END
|
|
|
|
DFT
|
|
XC B3LYP
|
|
CS00
|
|
END
|
|
|
|
TDDFT
|
|
NROOTS 12
|
|
END
|
|
|
|
TASK TDDFT ENERGY
|
|
</PRE>
|
|
|
|
<P>
|
|
<HR>
|
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<ADDRESS>
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Edoardo Apra
|
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2004-05-25
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</ADDRESS>
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