Dear all,
I have a question about the partial charge calculation for a molecular dynamics simulation using GAFF force field.
I have calculated the partial charges of the same molecule in two way:
a) GAUSSIAN+ resp (antechamber) b) GAMESS US + resp (molby)
Using the same molecule, the same level (HF 6-31G) I obtain slightly different values.
Gaussian input:
%NProcShared=4
%chk=molecule
#HF/6-31G* SCF=tight Test Pop=MK iop(6/33=2) iop(6/42=6) opt
Gamess input:
$CONTRL COORD=UNIQUE EXETYP=RUN ICHARG=0
ICUT=20 INTTYP=HONDO ITOL=30
MAXIT=200 MOLPLT=.T. MPLEVL=0
MULT=1 QMTTOL=1e-08 RUNTYP=OPTIMIZE
SCFTYP=RHF UNITS=ANGS NZVAR=48 $END
$SCF CONV=1.0E-06 DIRSCF=.T. FDIFF=.T.
DAMP=.T. $END
$STATPT NSTEP=400 OPTTOL=1.0E-06 PROJCT=.F. $END
$SYSTEM MEMDDI=0 MWORDS=16 TIMLIM=50000 $END
$GUESS GUESS=HUCKEL $END
$BASIS GBASIS=N31 NGAUSS=6 NDFUNC=1 $END
$ZMAT DLC=.T. AUTO=.T. $END
$ELPOT IEPOT=1 OUTPUT=PUNCH WHERE=PDC $END
$PDC CONSTR=NONE PTSEL=CONNOLLY $END
$DATA
Do you know which is the more correct and why are they different?
Best regards,
MV
If you use Multiwfn (http://sobereva.com/multiwfn) to compute RESP charge based on wavefunction of Gaussian and that of GAMESS-US, you can obtain exactly the same result.
Acrolein is taken as an example here. Relevant files have been uploaded as the compressed package, the acrolein.gjf is input file of Gaussian at HF/6-31G* level, the acrolein.fch is the resulting formatted checkpoint file. The acrolein.inp is input file of GAMESS-US at HF/6-31G* level, the acrolein.gms is corresponding output file.
After booting up Multiwfn, input following command to obtain RESP charge based on wavefunction of Gaussian
acrolein.fch // Load the file
7 // Population analysis
18 // RESP charge calculation
1 // Standard RESP charge using two-step fitting
Result:
1(O ) -0.5220534735
2(C ) 0.5508055396
3(C ) -0.2056248019
4(H ) -0.0027583012
5(H ) 0.1661025617
6(C ) -0.3898093673
7(H ) 0.2016689213
8(H ) 0.2016689213
Input following command to obtain RESP charge based on wavefunction of GAMESS-US
acrolein.gms
7
18
1
Result:
1(O ) -0.5220386267
2(C ) 0.5507824130
3(C ) -0.2056077318
4(H ) -0.0027536702
5(H ) 0.1660995198
6(C ) -0.3898308246
7(H ) 0.2016744603
8(H ) 0.2016744603
As you can see, the difference is completely negligible.
The difference of your results may come from different implementations of RESP charge fitting in the two codes, or different distribution of fitting points, or bug in the program.
Thanks both for the answers. I have tried Multiwfn , but I obtained a different result than Gaussian+antechamber. Anyway it could be a valid alternative.
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