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<!--Converted with LaTeX2HTML 99.2beta8 (1.43)
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original version by: Nikos Drakos, CBLU, University of Leeds
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* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
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* with significant contributions from:
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Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
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<title>Capabilities</title>
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<link rel="stylesheet" type="text/css" href="shared/nwchem_basic.css">
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<body bgcolor="FFFFFF">
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<table width="650">
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<tbody>
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<br>
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<table>
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<tbody>
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<td align="left" width="325"><img src="../images/nwchem_logo_dark.gif" border=0 width=200 alt="NWChem - computational chemistry on parallel computers"></td>
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<td align="right" width="325" valign="bottom">
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<a href="nwchem_main.html">NWChem Home</a> |
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<a href="disclaimer.html">Security & Privacy</a> |
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<a href="http://www.pnl.gov" target="_blank">PNNL</a>
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</td>
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</tr>
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</tbody>
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</table>
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<hr>
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<h1>NWChem 5.1 Functionality and Capabilities</h1>
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<br>
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<p>NWChem provides many methods to compute the properties of
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molecular and
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periodic systems using standard quantum mechanical descriptions of the
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electronic wavefunction or density. In addition, NWChem has the
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capability to perform classical molecular dynamics and free energy
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simulations. These approaches may be combined to perform mixed
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quantum-mechanics and molecular-mechanics simulations. </p>
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<p>NWChem is available on almost all high performance computing
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platforms,
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workstations, PCs running LINUX, as well as clusters of desktop
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platforms or
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workgroup servers. NWChem development has been devoted to providing
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maximum efficiency on massively parallel processors. It achieves this
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performance
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on the 1960 processors HP Itanium2 system in the EMSL's MSCF. It has
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not been optimized for high performance on single processor desktop
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systems.<span style="font-weight: bold;"><br>
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</span><a name="SECTION00610000000000000000"></a></p>
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<p></p>
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<h1><small><a name="SECTION00610000000000000000">1. Molecular
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electronic structure</a>
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</small></h1>
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<p>
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The following quantum mechanical methods are available to calculate
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energies, analytic first derivatives and second derivatives with
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respect to atomic
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coordinates. </p>
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<p></p>
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<ul>
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<li>Self Consistent Field (SCF) or Hartree Fock (RHF, UHF).
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</li>
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<li>Gaussian Density Functional Theory (DFT), using many local,
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non-local (gradient-corrected), and hybrid (local, non-local, and HF)
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exchange-correlation potentials (spin-restricted)
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with formal N<sup>3</sup> and N<sup>4</sup> scaling.
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</li>
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<li>Wide range of supported exchange, correlation, and GGA functionals. <A HREF="dft_functionals.html">Click for the full list.</A></li>
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</ul>
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<p>
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The following methods are available to calculate energies and analytic
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first derivatives with respect to atomic coordinates. Second
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derivatives are computed by finite difference of the first derivatives.
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</p>
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<p></p>
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<ul>
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<li>Self Consistent Field (SCF) or Hartree Fock (ROHF). </li>
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<li>Gaussian Density Functional Theory (DFT), using many local,
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non-local (gradient-corrected), and hybrid (local, non-local, and HF)
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exchange-correlation potentials (spin-unrestricted)
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with formal N<sup>3</sup> and N<sup>4</sup> scaling.
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</li>
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<li>Spin-orbit DFT (SODFT), using many local and non-local
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(gradient-corrected)
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exchange-correlation potentials (spin-unrestricted).
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</li>
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<li>MP2 including semi-direct using frozen core and RHF and UHF
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reference.
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</li>
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<li>Complete active space SCF (CASSCF).
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</li>
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</li>
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<li>Constrained DFT (CDFT)
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</li>
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</ul>
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<p>
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The following methods are available to compute energies only. First
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and second derivatives are computed by finite difference of the
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energies.
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</p>
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<ul>
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<li>CCSD, CCSD(T), CCSD+T(CCSD), with RHF reference.
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</li>
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<li>Selected-CI with second-order perturbation correction.
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</li>
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<li>MP2 fully-direct with RHF reference.
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</li>
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<li>Resolution of the identity integral approximation MP2
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(RI-MP2), with RHF and UHF reference.
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</li>
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<li>CIS, TDHF, TDDFT, and Tamm-Dancoff TDDFT for excited states
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with RHF, UHF, RDFT, or UDFT reference.
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</li>
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<li>CCSD(T) and CCSD[T] for closed- and open-shell systems (TCE
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module)
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</li>
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<li>UCCD, ULCCD, UCCSD, ULCCSD, UQCISD, UCCSDT, and UCCSDTQ
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with RHF, UHF, or ROHF reference.
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</li>
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<li>UCISD, UCISDT, and UCISDTQ with RHF, UHF, or ROHF
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reference.
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</li>
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<li>Non-canonical UMP2, UMP3, and UMP4 with RHF or UHF
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reference.
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</li>
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<li>EOM-CCSD, EOM-CCSDT, EOM-CCSDTQ for excitation energies,
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transition
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moments, and excited-state dipole moments of closed- and open-shell
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systems
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</li>
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<li>CCSD, CCSDT, CCSDTQ for dipole moments of closed- and
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open-shell
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systems
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</li>
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<li> Second order approximate coupled-cluster model with singles and
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doubles (CC2) for excited states in TCE
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</li>
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</ul>
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<p>
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The following methods can be used to calculate molecular properties:
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<ul>
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<li> Coupled-cluster linear response available using both restricted and unrestricted references
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</li>
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<li> Ground-state dynamic polarizabilities at the CCSD and CCSDT levels of theory using the linear response formalism
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</li>
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</ul>
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<p>
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For all methods, the following operations may be performed:
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</p>
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<ul>
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<li>Single point energy
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</li>
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<li>Geometry optimization (minimization and transition state)
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</li>
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<li>Molecular dynamics on the fully <em>ab initio</em>
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potential energy surface
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</li>
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<li>Numerical first and second derivatives automatically
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computed if analytic derivatives are not available
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</li>
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<li>Normal mode vibrational analysis in cartesian coordinates
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</li>
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<li>ONIOM hybrid method of Morokuma and co-workers
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</li>
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<li>Generation of the electron density file for graphical
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display
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</li>
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<li>Evaluation of static, one-electron properties.
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</li>
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<li>Electrostatic potential fit of atomic partial charges
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(CHELPG method with optional RESP restraints or charge constraints)
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</li>
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</ul>
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<p>
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For closed and open shell SCF and DFT:
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</p>
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<ul>
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<li>COSMO energies - the continuum solvation `COnductor-like
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Screening MOdel' of A. Klamt and G. Schüürmann to describe
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dielectric screening effects in solvents.
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</li>
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</ul>
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<p>
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In addition, automatic interfaces are provided to
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</p>
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<ul>
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<li>The natural bond orbital (NBO) package
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</li>
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<li>Python
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</li>
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</ul>
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<p>
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</p>
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<h1><small><a name="SECTION00620000000000000000">2. Relativistic
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effects</a>
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</small></h1>
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<p>
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The following methods for including relativity in quantum chemistry
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calculations are available:
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</p>
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<ul>
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<li>The spin-free one-electron Douglas-Kroll approximation is
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available for all quantum mechanical methods and their gradients.
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</li>
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<li>Dyall's spin-free Modified Dirac Hamiltonian approximation
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is available for the Hartree-Fock method and its gradients.
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</li>
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<li>One-electron spin-orbit effects can be included via
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spin-orbit potentials. This option is available for DFT and its
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gradients, but has to be run without symmetry.
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</li>
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<li>Spin-free and spin-orbit zeroth-order relativistic approximation (ZORA) for DFT
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</li>
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</ul>
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<p>
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</p>
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<h1><small><a name="SECTION00630000000000000000">3.
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Pseudopotential plane-wave electronic structure</a>
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</small></h1>
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<p>
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Two modules are available to compute the energy, optimize the
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geometry, numerical second derivatives, and perform ab initio molecular
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dynamics using pseudopotential plane-wave DFT.
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</p>
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<p></p>
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<ul>
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<li>PSPW - (Pseudopotential plane-wave) A gamma point code for
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calculating
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molecules, liquids, crystals, and surfaces.
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</li>
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<li>Band - A prototype band structure code for calculating
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crystals and surfaces with small band gaps (e.g. semi-conductors and
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metals)
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</li>
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</ul>
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<p>
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With
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</p>
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<p></p>
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<ul>
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<li>Conjugate gradient and limited memory BFGS minimization
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</li>
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<li>Car-Parrinello (extended Lagrangian dynamics)
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</li>
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<li>Constant energy and constant temperature Car-Parrinello
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simulations
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</li>
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<li>Fixed atoms in cartesian and SHAKE constraints in
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Car-Parrinello
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</li>
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<li>Pseudopotential libraries
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</li>
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<li>Hamann and Troullier-Martins norm-conserving
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pseudopotentials with optional semicore corrections
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</li>
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<li>Automated wavefunction initial guess, now with LCAO
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</li>
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<li>Vosko and PBE96 exchange-correlation potentials
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(spin-restricted and unrestricted)
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</li>
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<li>Orthorhombic simulation cells with periodic and
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free space boundary conditions.
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</li>
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<li>Modules to convert between small and large plane-wave
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expansions
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</li>
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<li>Interface to DRIVER, STEPPER, and VIB modules
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</li>
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<li>Polarization through the use of point charges
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</li>
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<li>Mulliken, point charge, DPLOT (wavefunction, density and
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electrostatic
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potential plotting) analysis
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<li> Fermi smearing added to BAND </li>
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<li> Two-component wavefunctions added to BAND </li>
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<li> HGH spin-orbit potentials added to BAND </li>
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<li> Hilbert decomposed parallel FFT added to BAND </li>
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<li> Car-Parrinello QM/MM added to PSPW </li>
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<li> Wannier orbital generation now works with non-cubic cells </li>
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<li> New parallel decomposition in which both the FFT grid and orbitals are
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distributed has been implemented in PSPW
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</li>
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</ul>
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<p>
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</p>
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<h1><small><a name="SECTION00640000000000000000">4. Molecular
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dynamics</a>
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</small></h1>
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<p>
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The following functionality is available for classical molecular
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simulations:
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</p>
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<ul>
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<li>Single configuration energy evaluation
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</li>
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<li>Energy minimization
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</li>
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<li>Molecular dynamics simulation
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</li>
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<li>Free energy simulation (multistep thermodynamic
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perturbation (MSTP) or multiconfiguration thermodynamic integration
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(MCTI) methods with options of single and/or dual topologies, double
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wide sampling, and separation-shifted scaling)
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</li>
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</ul>
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<p>
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The classical force field includes:
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</p>
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<ul>
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<li>Effective pair potentials (functional form used in AMBER,
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GROMOS, CHARMM, etc.) </li>
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<li>First order polarization
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</li>
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<li>Self consistent polarization
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</li>
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<li>Smooth particle mesh Ewald (SPME) </li>
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<li>Twin range energy and force evaluation </li>
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<li>Periodic boundary conditions
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</li>
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<li>SHAKE constraints </li>
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<li>Consistent temperature and/or pressure ensembles
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</li>
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</ul>
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<p>
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NWChem also has the capability to combine classical and quantum
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descriptions in order to perform:
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</p>
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<ul>
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<li>Mixed quantum-mechanics and molecular-mechanics (QM/MM)
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minimizations and molecular dynamics simulation , and
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</li>
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<li>Quantum molecular dynamics simulation by using any of the
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quantum mechanical methods capable of returning gradients.
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</li>
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</ul>
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<p>
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By using the DIRDYVTST module of NWChem, the user can write an input
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file to the POLYRATE program, which can be used to calculate rate
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constants including quantum mechanical vibrational energies and
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tunneling
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contributions.
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</p>
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<p></p>
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<h1><small><a name="SECTION00650000000000000000">5. Python</a>
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</small></h1>
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<p>
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The Python programming language has been embedded within NWChem and
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many of the high level capabilities of NWChem can be easily combined
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and controlled by the user to perform complex operations.
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</p>
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<p></p>
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<h1><small><a name="SECTION00660000000000000000">6. Parallel
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tools and libraries (ParSoft)</a>
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</small></h1>
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<p>
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</p>
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<ul>
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<li>Global arrays (GA)
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</li>
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<li>Aggregate Remote Memory Copy Interface (ARMCI)
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</li>
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<li>Linear Algebra (PeIGS) and FFT
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</li>
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<li>ParIO
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</li>
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<li>Memory allocation (MA)
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</li>
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</ul>
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<p></p>
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<hr>
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Contact: <a href="mailto:ms3distribution@emsl.pnl.gov">NWChem Support</a><br>
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Updated: Dec., 2007
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</td>
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</tr>
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</tbody>
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</table>
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</body>
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</html>
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