Dear Q-Chem community,
I am using Q-Chem version 5.4.0 to perform a partial Hessian vibrational analysis, and I would like to calculate anharmonic (TOSH and VPT2) frequencies for the vibrational modes found in the harmonic partial Hessian calculation. From reading the Q-Chem manual, it seems like this is possible, but there are no examples.
Below I include a representative input file for a successful partial Hessian harmonic frequency calculation:
$molecule 0 1 H 0.0000000000 0.0000000000 1.6627839987 C 0.0000000000 0.0000000000 0.5996740432 C 0.0000000000 0.0000000000 -0.5996740432 H 0.0000000000 0.0000000000 -1.6627839987 $end $rem BASIS = 6-311++G** METHOD = B3LYP JOB_TYPE = freq SCF_CONVERGENCE = 10 SCF_ALGORITHM = RCA_DIIS THRESH = 14 XC_SMART_GRID = True XC_GRID = 000099000590 PHESS = True N_SOL = 3 $end $alist 1 2 3 $end
The Q-Chem manual indicates that I can follow a partial Hessian calculation with VPT2 and TOSH anharmonic frequency calculations, so I tried adding the keyword ANHAR = True to the $rem section of the above input file, but I received the following error:
Q-Chem fatal error occurred in module libmdc/newfileman.C, line 384: FileMan error: End of file reached prematurely reading (1152) bytes in file FILE_NORMAL_MODE
Any guidance to help me calculate anharmonic frequencies for a partial Hessian is very much appreciated!