All Questions
Tagged with computational-chemistry reference-request
23
questions
22
votes
1
answer
970
views
DFT Code for Atoms : Sources
Some time ago I implemented the restricted and unrestricted Hartree-Fock methods. I had a lot of fun and I learned a lot. It goes without saying that Szabo and Ostlund's book "Modern Quantum Chemistry"...
19
votes
3
answers
736
views
Do modern dispersion-corrected DFT methods give more accurate molecular geometries?
I was discussing with a colleague the use of modern dispersion-corrected density functionals. I take it almost as a given that the methods generally produce "better" (for some definition) geometries, ...
18
votes
3
answers
5k
views
Modern open-source tools for simulation of NMR spectra
I am interested in predicting the NMR spectrum of small organic compounds. It doesn't matter to me if the prediction is very accurate. I'll eventually be comparing the prediction to experimental ...
13
votes
1
answer
1k
views
Why does bond length decrease with increased basis set quality for SCF methods?
From Reviews in Computational Chemistry Vol. 5, for $\ce{H2O}$ using HF, MP2, CCSD, and CCSD(T), all lengths in angstroms:
$$
\small
\begin{array}{rcccc}
\text{Basis} & \text{HF} & \text{MP2}...
11
votes
1
answer
593
views
Database for molecular dipole transition moments?
I'm looking for the dipole transition matrix elements for electronic transitions between the ground and excited states of the carbon dioxide cation, $\text{CO}_2^+$, that is, objects like
$$\langle\...
10
votes
3
answers
851
views
What is Nesbet's theorem?
In a talk by Frank Neese there was a slide with title "Nesbet's theorem" and an equation indicating something like "if your wavefunction has the double excitation amplitudes correct, then you can get ...
10
votes
3
answers
981
views
Free chemical database to search for physical properties?
I am looking for an Open-access tool that can search "backwards", eg. give me all the structures corresponding to a given heat of formation, critical pressure, etc. It would be even better if the ...
9
votes
3
answers
2k
views
InChIKey generation from InChI
I am trying to find some good resources to understand generation of InChIKeys from the InChI. There seems to be no resource available online. I have gone through the Wikipedia article for InChI, but ...
9
votes
0
answers
898
views
Free Web-Based Orbital Solver to look into the Walsh orbitals of a perturbed cyclopropane
There exists a free online orbital calculator.
When I draw cyclopropane it plots three molecular orbitals, but unfortunately it doesn't use the Walsh orbitals.
Are there any free online tools which ...
8
votes
1
answer
402
views
Tunneling corrections in reaction rates
I've studied Transition State Theory since I asked this a while ago, but so far I have not been able to find a detailed explanation of how tunneling corrections are implemented into reaction rates ...
8
votes
1
answer
2k
views
Difference between single point energy and dimerization energy
I am investigating potential energy surface characteristics of some electrostatic monomeric interactions e.g. $\ce{F-H}$...$\ce{F-H}$.
I'm using DFT and SCS-MP2 to perform the necessary calculations ...
8
votes
3
answers
282
views
Is it wise to use ECPs on light atoms for electronic structure calculations?
So, I have a big organic molecule consisting of $\ce{H}$, $\ce{C}$, $\ce{O}$, and $\ce{N}$ atoms and the goal is to find its equilibrium geometry and US/Vis spectrum. The molecule is so big that I was ...
6
votes
1
answer
1k
views
Carbohydrate configurations
I want to study several carbohydrates that includes but not limited to the following molecules:
Glucose
Galactose
Mannose
Fructose
Tagatose
Sorbose
I know that for any carbohydrate, possible list of ...
6
votes
0
answers
278
views
Where to find experimental spin-orbit coupling constants?
I am searching for experimental spin-orbit coupling constants, particularly for main group elements and Cr(0) to calculate correlation consistent Composite Approach (ccCA) energetics. This method ...
5
votes
1
answer
216
views
Quotable Literature for the Enthalpy of a Proton
A proton obviously has no electronic energy, no vibrational and no rotational degrees of freedom. Therefore I think it is fair to assume, that $$H(\ce{H+})=\frac32\cdot \mathcal{R}\cdot T$$ holds for ...