All Questions
Tagged with quantum-chemistry software
55
questions
1
vote
0
answers
28
views
Gaussian Program Error for Linear Triatomic Molecule
I am trying to calculate the Hessian and vibrational frequencies of OCS (and eventually some anharmonic properties) with Gaussian09. However, the program always fails and I end up with the following ...
- 111
1
vote
0
answers
67
views
Hartree-Fock calculations of the states of Nitrogen molecule ion
I was reading the third chapter of "Modern Quantum Chemistry" by A. Szabo and N. Ostlund about HF calculations, and in the end of the chapter it shows as an example a calculation on $\ce{N2}$...
- 461
10
votes
2
answers
408
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Software to draw one-dimensional PES including vibrational energy levels
I am trying to represent the difference between the an anharmonic and harmonic treatment of vibrations. The easiest way to do this is to present an example of a harmonic and anharmonic potential ...
- 554
5
votes
1
answer
335
views
How to compute the electronic energy reported by Gaussian from the AlphaOrbitalEnergies?
I followed the instructions on Wolfram Language & System Documentation Center — FCHK (.fchk) to analyze the *.fchk file.
I ran an energy calculation with ...
3
votes
1
answer
288
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Quantum chemistry Python package to solve the Coupled-Perturbed Hartree–Fock equations
Two of the most well-known Python quantum chemistry pakcages, PySCF and Psi4, can solve the Hartree–Fock equations. However, I am interested in finding analytic derivatives of the electron integrals:
$...
- 131
7
votes
1
answer
1k
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ORCA: How to plot an adiabatic potential in dihydrogen H2 molecule?
I stared to study ORCA, and I try to obtain classical results for dihydrogen as for example. I need to get a starting point to understand what needs to be done.
So, How to plot an adiabatic potential ...
- 935
5
votes
1
answer
151
views
Which quantum chemistry approximation to use?
I'm just getting started with quantum chemistry using some simple test problems. I have a few of the software packages installed (ASE, Psi4, GPAW etc) and everything is working - no issues with the ...
- 283
1
vote
1
answer
512
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Computational chemistry software to generate files of cartesian coordinates and zmatrix of molecules
Is there any software that I can provide bond lengths, bond angles and torsion dihedrals of a molecule and generate an output file in the format of cartesian coordinates or zmatrix?
Example:
I would ...
- 311
2
votes
0
answers
803
views
How do you optimize an organo-metalic compound containing cerium in in Gaussian?
I am trying to perform optimisation of the molecule attached. I need to get partial charges and frequencies. The issue is that it doesn't converge with following input:
...
3
votes
1
answer
171
views
I'd like to model some compounds with DFTB, but some elements don't have parameter files in the official site. Is there a workaround?
I was reading a bit about this technique, Density Functional based Tight binding (DFTB). It's claimed it can provide a speed improvement of several fold when compared to plain DFT, still giving ...
- 663
1
vote
0
answers
152
views
What are the alternatives we have to the VEDA 4 vibrational energy distribution analysis software?
Said software is very useful when you need to assign the peaks in vibrational spectra to different vibrational modes found in a hessian calculation for a given molecule, as described in Jamróz, Michał ...
- 663
6
votes
1
answer
175
views
Are there any semiempirical methods that work with heavy alkaline earth metals?
I did some research. Found some semiempirical methods that work even with heavy lanthanide compounds (RM1). But could not find any references to semiempirical methods compatible with the heavier ...
- 663
2
votes
1
answer
2k
views
How to reproduce the Gaussian 09 SDD basis set in Gamess-US?
I'm trying to migrate away from Gaussian 09, using Gamess-US instead for molecular modelling of some heavy alkaline earth metal complexes, using density functional theory (DFT). In some of my previous ...
- 663
6
votes
4
answers
1k
views
Software recommendations for overlaying molecular structures
I am looking for a program to overlay the structures of small molecules as an aid for my students in comparing the results of optimization geometries using different optimization methods.
At this ...
- 1,061
3
votes
1
answer
138
views
How to access implicit bond angles that don't appear in Gaussian's z-matrix input?
Suppose I have a Gaussian script to calculate the energy of a relatively large molecule like hexamethyldisiloxane:
...
- 311