diff --git a/doc/user/dft.tex b/doc/user/dft.tex index da2a22b897..11ab165426 100644 --- a/doc/user/dft.tex +++ b/doc/user/dft.tex @@ -1,5 +1,5 @@ % -% $Id: dft.tex,v 1.92 2007-02-13 23:47:25 bert Exp $ +% $Id: dft.tex,v 1.93 2007-02-14 21:58:12 bert Exp $ % \label{sec:dft} @@ -978,7 +978,64 @@ active, you need to use the following line CONVERGENCE rabuck 30 \end{verbatim} +\section{{\tt CDFT} --- Constrained DFT} +\label{cdft} +This option enables the constrained DFT formalism by Wu and Van Voorhis described +in the paper: Q. Wu, T. Van Voorhis, Phys. Rev. A {\bf 72}, 024502 (2005). + +\begin{verbatim} + CDFT [] (charge||spin ) \ + [pop (becke||mulliken||lowdin) default lowdin] +\end{verbatim} + +Variables fatom1 and latom1 define the first and last atom of the group of atoms to which +the constaint will be applied. Therefore the atoms in the same group should be placed +continuously in the geometry input. If fatom2 and latom2 are specified, the difference between +group 1 and 2 (i.e. 1-2) is constrained. + +The constraint can be either on the charge or the spin density (# of alpha - beta electrons) with +a user specified constaint_value. Note: No gradients have been implemented for the spin constaints +case. Geometry optimizations can only be performed using the charge constaint. + +To calculate the charge or spin density, the Becke, Mulliken, and Lowdin population schemes can be +used. The Lowdin scheme is default while the Mulliken scheme is not recommended. If basis sets with +many diffuse functions are used, the Becke population scheme is recommended. + +Multiple constaints can be defined simultaniously by defining multiple {\tt cdft} lines in the input. +The same population scheme will be used for all constaints and only needs to be specified once. If +multiple population options are defined, the last one will be used. When there are convergence +problems with multiple constaints, the user is advised to do one constraint first and to use the +resulting orbitals for the next step of the constained calculations. + +It is best to put "convergence nolevelshifting" in the dft directive to avoid issues with gradient +calculations and convergence in CDFT. Use orbital swap to get a broken-symmetry solution. + +An input example is given below. + +\begin{verbatim} +geometry +symmetry +C 0.0 0.0 0.0 +O 1.2 0.0 0.0 +C 0.0 0.0 2.0 +O 1.2 0.0 2.0 +end + +basis +* library 6-31G* +end + +dft + xc b3lyp + convergence nolevelshifting + odft + mult 1 + vectors swap beta 14 15 + cdft 1 2 charge 1.0 +end +task dft +\end{verbatim} \section{{\tt SMEAR} --- Fractional Occupation of the Molecular Orbitals} \label{smear}