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2019-05-10T17:26:10Z

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== Setup Q-Chem ==
First ensure that Q-Chem is installed:
if
qchem
gives
Need at least to specify the input file.
Usage: qchem [ -save ] [ -np procs ] infile [ outfile ] [ dir ]
then skip to the next section. Otherwise you will need to add the following line to your ~/.bashrc file, and then source your ~/.bashrc
. ~ajwt3/code/qchem/qcsetup.bash

== H<sub>2</sub>O test ==

create a new directory with the following files
h2o.inp
$comment
water HF 3-21G* Single point energy
$end

$molecule
0 1
O -0.4160001815 0.0000000000 0.0454252753
H -0.9343018760 0.0000000000 -0.8673296731
H 0.3503028923 0.0000000000 0.0194028911
$end

$rem
EXCHANGE HF Exact exchange
BASIS 3-21G* Basis Set
SCF_CONVERGENCE 8 Tight convergence
jobtype force
sym_ignore true
$end
h2o
$comment
water HF 3-21G* Single point energy
$end

$molecule
0 1
O -0.4160001815 0.0000000000 0.0454252753
H -0.9343018760 0.0000000000 -0.8673296731
H 0.3503028923 0.0000000000 0.0194028911
$end

$rem
scf_guess read
EXCHANGE HF Exact exchange
BASIS 3-21G* Basis Set
SCF_CONVERGENCE 8 Tight convergence
jobtype force
sym_ignore true
$end
and odata
STEPS 20
DEBUG
QCHEM 'qchem -save' 'h2o' 'h2osavedir'
BFGSMIN 1.0D-5
POINTS

h2o.inp will be used to create an initial scf calculation which will be used to restart the OPTIM runs
qchem -save h2o.inp h2o.out h2osavedir
This will create h2o.out as well as $QCSCRATCH/h2osavedir where the converged calculation will save its files. Without the -save, Q-Chem will delete its working files.
Check that it's actually worked:
ajwt3@dexter:~/calc/qchem_optim_test/test1$ tail h2o.out
Total job time: 0.12s(wall), 0.11s(cpu)
Wed Sep 18 17:44:58 2013

*************************************************************
* *
* Thank you very much for using Q-Chem. Have a nice day. *
* *
*************************************************************
If not then email me to work out what's wrong.

Now we can inspect the QCHEM line of the odata file. The first option is how to run Q-Chem. The second is the input file name, and the third is Q-Chem's working directory.
The only difference between h2o and h2o.inp is that the former includes the line
scf_guess read
which indicates it should restart from the previous calculation.

Now you can run OPTIM and sit back and relax.

OPTIM/Q-Chem Tutorial - Revision history

Adk44: Created page with "== Setup Q-Chem == First ensure that Q-Chem is installed: if qchem gives Need at least to specify the input file. Usage: qchem [ -save ] [ -np procs ] infile [ outfile ]..."