13
votes
Accepted
How to get potential energy surface from GAMESS?
I know it is easy to get the PES tabulated very neatly in MOLPRO with a command like:
{table,r,scf,ccsd,ccsd_t
head, R,HF-SCF,CCSD,CCSD(T)
sort,1,2,3}
which for ...
- 31.6k
11
votes
What is the difference between orbital localisation and NBO?
Note: This was a response I've originally written on Chemistry Stack Exchange, so it was intended to be very brief.
Natural Bond Orbital Theory is basically (among plenty of other uses) providing an ...
- 1,561
9
votes
How is "basis set projection" done?
What you're describing is very common, and is not limited to GAMESS and Q-Chem.
First, here's how to do it in MOLPRO, MRCC, GAMESS, Q-Chem (in fact the only electronic structure software that I ...
- 31.6k
9
votes
How to get potential energy surface from GAMESS?
It's not the simplest alternative, but sometimes to learn a bit of regular expressions and one scripting language can help a lot in tasks like this. It's a really worth time investment, if you have a ...
- 3,878
8
votes
Accepted
Alternatives to VEDA 4 vibrational energy distribution analysis software?
LocVib (part of MoViPac)
I have never used VEDA before, but according to the paper, it decomposes the normal modes into vibrations of atomic groups, bond stretching, bending or something else. ...
- 1,094
8
votes
Accepted
Which software is good with generally contracted basis sets?
General vs segmented contraction
Unless one is using a fully decontracted a.k.a "primitive" basis set, one uses contracted Gaussian-type orbitals (cGTOs), which are given as a linear ...
- 16.9k
8
votes
Which software is good with generally contracted basis sets?
Integral Screening
It is possible to place upper bounds on integrals based on the Cauchy-Schwartz inequality:
$$
\left( a a | b b \right) \ge \left( a c | b d \right)
$$
If the first integral is ...
- 1,603
8
votes
Accepted
What is the difference between orbital localisation and NBO?
In short, natural atomic orbitals are the orbitals you get from diagonalizing the one-particle reduced density matrix. One can then localize this set of orbitals via some maximization criteria. ...
- 3,329
8
votes
Accepted
Mismatched number of normal modes calculation in GAMESS
Firstly, a minor correction: a non-linear molecule has 3N-6 normal modes, not 3N-5 modes. Linear molecules have 3N-5 normal modes.
GAMESS automatically prints out some values in normal coordinate ...
- 6,276
8
votes
Accepted
How are molecular orbitals constructed from the coefficients and basis set?
Things are more clear to me when I look at the basis set in CFOUR format, because of the information at the top which tells me how many primitives and how many contractions there are for each type of ...
- 31.6k
8
votes
Accepted
How is "basis set projection" done?
Supplementing Nike's answer above.. This is actually quite elementary math. Let's say I have an orbital in a basis
$|\psi\rangle = \sum_i c_i |i\rangle$ and I want to find the expansion in some other ...
- 16.9k
8
votes
Accepted
The number of orbitals in Gaussian/GAMESS log file
As Nike mentioned, most basis sets produce more orbitals than the minimal set that you tend to think of for these elements. We can see how this works out for 6-31G(d,p) by looking at how the basis set ...
- 14.7k
7
votes
The number of orbitals in Gaussian/GAMESS log file
Yes, a good basis set will contain virtual (unoccupied) orbitals, in addition to the orbitals that are occupied by electrons.
Almost always: the larger the basis set, the more accurate the ...
- 31.6k
6
votes
Accepted
Optimization and vibrational analysis of excited state CO using GAMESS
I cannot see your output file, but I am pretty sure that the program is running into an error when starting the optimization i.e. when it is trying to generate the guess hessian.
You are using ...
- 6,276
6
votes
How to freeze molecular orbitals in GAMESS-US?
Firstly, the error NO $VEC INPUT FOUND means that GAMESS did not find molecular orbitals to read in. This is because you wrote two spaces before ...
- 381
6
votes
Which software is good with generally contracted basis sets?
MOLPRO
Continuing Susi's excellent benchmarking for $\ce{Zn}$ and $\ce{Zn_2}$, MOLPRO 2012 gives for $\ce{Zn}$:
...
- 31.6k
5
votes
Accepted
Excited state normal mode frequency doesn't match for NH3
This is not a full answer, because it does not solve the problem. But I hope to shed some light on why you are not getting the correct frequencies.
Short answer: I suspect there is a bug in GAMESS
...
- 6,276
5
votes
Excited state normal mode frequency doesn't match for NH3
I can see two major problems:
CCD != CC2 and I'm not certain if CC2 is available in GAMESS. CC2 is an approximation of CCSD, which is available in GAMESS. You may be able to use this since $\ce{NH3}$ ...
- 14.7k
5
votes
Accepted
GAMESS(US) Hessian calculation sometimes does not produce the IR intensities
I was able to figure out what was going wrong, but forgot to check back here and leave an answer if none were give.
@ShoubhikRMaiti should be credited with helping me figure this out. From this ...
- 1,202
5
votes
How is "basis set projection" done?
Note: I have corrected some omissions from my initial answer to avoid any confusion. For a rigorous explanation of the process, I would recommend looking at Susi's answer.
The projection process for ...
- 14.7k
5
votes
Accepted
What are the trade-offs setting DIRSCF to either .TRUE. or .FALSE. (the default) in GAMESS (US)?
I would say the reason that they default to storing the integrals is because there is no obvious choice to make one way or the other as it depends a lot on what resources are available and how large ...
- 3,329
5
votes
SCF not converging during RHF/STO-3G geometry optimisation
Based on your input file, I tried to run the calculation in my machine. As you didn't specified how did you obtain the original structure (assembled by hand or downloaded from structure database), I ...
- 3,878
5
votes
SCF not converging during RHF/STO-3G geometry optimisation
If you look at your last five iterations, you will see that the density change (which is what matters most for SCF convergence) is getting smaller in each iteration, meaning that the calculation is ...
- 31.6k
5
votes
Accepted
Computing analytic derivatives of molecular Hamiltonians obtained from solving Hartree-Fock equations
PySCF and Psi4 both implement analytical geometric Hessians for Hartree-Fock calculations. The computation of the geometric Hessian indeed requires solving the coupled perturbed Hartree-Fock equations:...
- 16.9k
4
votes
The number of orbitals in Gaussian/GAMESS log file
I should complement Nike and Tyberius' answers by the simple statement that e.g. hydrogen only consists of a single S function for the non-interacting atom. When the atomic symmetry is lifted, you get ...
- 16.9k
3
votes
Accepted
Energy decomposition analysis (EDA) at transition state
Very interesting question. I have no experience doing EDA, but as I'll probably need to do it in the future, I used your question as a starting point to learn more about it. I did some research, but ...
- 3,878
3
votes
Excited states using ORMAS flag in GAMESS
As specified in the GAMESS Documentation:
nspace=n means the active space will be split into $n$ groups.
mstart sets the ...
- 14.7k
2
votes
Error when trying to compile (after everything else has been done) GAMESS on Windows/WSL
I installed GFortran 9.4 and re-ran the compall file. The compilation succeeded but the gamess.00.x file was missing and GAMESS ...
- 846
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