Run

The computation of \(v_{cond}(\mathbf{r})\) is done in two major steps

• compute a CI wavefunction GAMESS-US for your molecule
• use the CI wavefunction to compute $$v_{cond}(\mathbf{r})$$ with vcond.exe

To demonstrate the usage of the v_cond package we give an example for the Hydrogen molecule.

Run GAMESS-US

We compute a FullCI wavefunction in an aug-cc-pVTZ basis set. Use the GAMESS-US input file h2_aug-cc-pVTZ_FCI.inp from v_cond/examples/h2_aug-cc-pVTZ_FCI or create it with the content

 $CONTRL
   SCFTYP=RHF
   CITYP=ALDET
   RUNTYP=ENERGY
   ISPHER=1
!   EXETYP=CHECK
 $END
 $SYSTEM
   TIMLIM=1000000
   mwords=100
 $END
 $CIINP
   NRNFG(6)=1
 $END$
 $CIDET
   NCORE=0
   NACT=45
   NELS=2
 $END
 $BASIS
   GBASIS=ACCT
 $END
 $GUESS
   GUESS=HUCKEL
 $END
 $DATA
H2 RHF/aug-cc-pVTZ+FULLCI exp. geom
Dnh 4

HYDROGEN 1.0 0.0 0.0 0.373
 $END

Execute GAMESS-US

rungmsvcond h2_aug-cc-pVTZ_FCI.inp > h2_aug-cc-pVTZ_FCI.out

Run vcond.exe

First we process the GAMESS-US output to create the vcond.exe input by using the cinput.sh script. This script can be found in the v_cond source directory. If desired, link cinput.sh to your ~/bin folder for easy execution

ln -s ~/path_to_v_cond/v_cond/scripts/cinput.sh ~/bin/.

Consider to add execute permissions to cinput.sh

chmod u+x ~/path_to_v_cond/v_cond/scripts/cinput.sh

Now we are ready to create the vcond.exe input by calling

cinput.sh h2_aug-cc-pVTZ_FCI.out

This will create the files vcond.basis and vcond.input. Additionally you will need to provide the file vcond.grid with the points at which \(v_{cond}(\mathbf{r})\) needs to be computed. For our example you can find a vcond.grid v_cond/examples/h2_aug-cc-pVTZ_FCI/, to compute \(v_{cond}(\mathbf{r})\) along the bond axis.

In the final step we call

vcond.exe

The files vcond.dat, density.dat, rhovcond.dat, vhartr.dat and wXC.dat are generated. wXC.dat contains the exchange-correlation energy density in the gauge of the exchange-correlation hole. See J. Chem. Theory Comput. 8, 3097 (2012) [pdf] [doi] for more details.