Quantum Chemistry Modeling Packages
LModeA-nano can directly read the formatted checkpoint file generated by Gaussian and Q-Chem. Other quantum chemistry modeling packages (e.g. ORCA, xtb) requires the formatted data file generated by UniMoVib.
Note
LModeA-nano can do basic local mode analysis for bond length and bond angles. More advanced analysis including decomposition of normal modes, adiabatic connection scheme and other internal coordinates are supported only by LModeA code.
Gaussian
Tested with Gaussian 16.
Perform an OPT+Freq calculation to do geometry optimization and then vibrational analysis.
%chk=ben.chk
%nproc=36
#p hf/6-31g opt freq geom=connectivity
Title Card Required
0 1
C -0.54491017 1.16167665 0.00000000
C 0.85024983 1.16167665 0.00000000
C 1.54778783 2.36942765 0.00000000
C 0.85013383 3.57793665 -0.00119900
C -0.54469117 3.57785865 -0.00167800
C -1.24229217 2.36965265 -0.00068200
H -1.09466917 0.20935965 0.00045000
H 1.39975783 0.20916365 0.00131500
H 2.64746783 2.36950765 0.00063400
H 1.40033383 4.53007965 -0.00125800
H -1.09481317 4.53013965 -0.00263100
H -2.34189617 2.36983565 -0.00086200
1 2 1.5 6 1.5 7 1.0
2 3 1.5 8 1.0
3 4 1.5 9 1.0
4 5 1.5 10 1.0
5 6 1.5 11 1.0
6 12 1.0
7
8
9
10
11
12
Please check the vibrational frequencies to make sure that the molecular structure is at a local minimum point.
The %chk
is a must to first produce checkpoint file. Convert it to formatted one with
$ formchk ben.chk
The corresponding .fchk
file is then generated. Then follow the instructions in quickstart example to do local mode analysis with LModeA-nano.
Q-Chem
Tested with Q-Chem 5.1.0
Given an optimized molecular structure, perform vibrational analysis
$comment
water freq
$end
$molecule
0 1
O -0.000001 -0.000001 -0.408455
H 0.758758 -0.000004 0.204225
H -0.758756 0.000004 0.204230
$end
$rem
MEM_TOTAL 100000
BASIS cc-pVDZ
METHOD b3lyp
xc_grid 75000302
UNRESTRICTED FALSE
JOBTYPE freq
THRESH 14
SCF_CONVERGENCE 10
GUI 2
$end
GUI 2
asks Q-Chem to produce the formatted checkpoint file .fchk
. Always check the vibrational frequencies before doing local mode analysis.
Then follow the instructions in quickstart example to do local mode analysis with LModeA-nano.
Other Packages
To perform local mode analysis based on the calculation results by other quantum chemistry packages, the UniMoVib package should be installed first.
The workflow is
Perform vibrational analysis on an optimized molecular structure with a quantum chemistry package (e.g. ORCA, xtb)
Run UniMoVib to generate a formatted data file
.umv
by parsing the output file in the last stepLoad the
.umv
file to LModeA-nano for local mode analysis
A complete list of supported quantum chemistry packages by UniMoVib can be found at https://github.com/zorkzou/UniMoVib.
In this tutorial, ORCA 4 is used as an example.
The vibrational analysis of an optimized molecular structure with ORCA 4 produces an .hess
file. Compose an input file job.inp
for UniMoVib
a test job
$contrl
qcprog="orca"
ifsave=.true.
$end
$qcdata
fchk="h2o.hess"
$end
ifsave=.true.
saves a formatted data file .umv
. Running UniMoVib with above input, it produces job.umv
.
Compose an input file unimovib.inp
for LModeA-nano
@unimovib
UMV = job.umv
Follow these steps to perform local mode analysis with LModeA-nano
open a new PyMOL window and launch LModeA-nano by clicking Plugin → LModeA-nano
click the … (Browse) button and select the
unimovib.inp
filechange the program drop-down list from VASP to UniMoVib
click Load
change Dimensions to
0
and click Confirm button
Then local mode analysis can be performed as described in quickstart examples.