5.3 Overview of Available Functionals

5.3.7 Semi-Empirical Functionals

The following semi-empirical methods are available in Q-CHEM:

  • HF-3c: It is an HF-based semi-empirical method which is used with a minimal basis called MINIX. All the elements from H to Xe are supported. For the elements from Rb (Z = 37) to Xe (Z = 54), def2-ECP has to be used.Sure:2013

  • PBEh-3c: It is a DFT based method which is used with def2-mSVP basis set.This is available for all the elements from H to Rn. For the elements from Rb (Z = 37) to Rn (Z = 86), def2-ECP has to be used. It is a more accurate method than HF-3c as it has correlation.Grimme:2015

Example 5.4  Q-Chem input for HF-3c method.

$molecule
0 1
O  -1.551007  -0.114520   0.000000
H  -1.934259   0.762503   0.000000
H  -0.599677   0.040712   0.000000
O   1.350625   0.111469   0.000000
H   1.680398  -0.373741  -0.758561
H   1.680398  -0.373741   0.758561
$end

$rem
   JOB_TYPE = SP
   SCF_CONVERGENCE = 8
   BASIS  =  MINIX
   METHOD = HF3C
   SCF_GUESS = SAD
$end

Example 5.5  Q-Chem input for PBEh-3c method.

$molecule
0 1
O  -1.551007  -0.114520   0.000000
H  -1.934259   0.762503   0.000000
H  -0.599677   0.040712   0.000000
O   1.350625   0.111469   0.000000
H   1.680398  -0.373741  -0.758561
H   1.680398  -0.373741   0.758561
$end

$rem
jobtype sp
method  PBEh-3c
basis def2-mSVP
xc_grid 000099000590
incdft 0
incfock 0
scf_convergence 8
thresh 14
symmetry false
sym_ignore true
$end