Unanswered Questions
496 questions with no upvoted or accepted answers
5
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answers
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How to derive a state symmetry in D2h point group from its wavefunction?
Let's have an atomic carbon with the following electron configuration:
$$
1s^2 2s^2 2p^2
$$
One of it's levels is ${}^1S_0$, which is corresponding with the following state:
$$
\begin{align}
\left| ...
- 1,267
5
votes
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74
views
Identifying principal quantum numbers in natural population analysis
Following a Hartree-Fock calculation, I would like my program to perform some kind of Natural Bond Orbital (NBO) analysis. Preceding this I would like to output a list of atomic orbitals, along with ...
- 1,271
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321
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Why is spin-contamination undesirable?
Why is spin-contamination, introduced by e.g. Unrestricted Hartree Fock, undesirable, and to which problems further on can it lead?
The only problem I currently see myself is that spin-contamined ...
- 1,696
5
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168
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How to calculate a molecule's oscillator strength?
I was wondering how to calculate a molecule's (e.g. biphenyl) oscillator strength using a very simplified model.
If I want to calculate a molecule's excited states a good start is something like a ...
- 369
5
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93
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MCSCF Hessian transformation
I have tried doing the transformation of the Hessian in MCSCF following the notation that is used in Molecular Electronic-Structure Theory (MEST). Here I try to show what steps I have taken (to get ...
- 2,242
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172
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When is it necessary to consider size consistency?
For what kinds of reactions is it essential to account for size consistency? To my understanding for dissociation reactions $(\ce{AB -> A + B})$ it is important to consider. However, is it also ...
- 17.4k
5
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100
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Methodology and basis set for study in UV-Vis
I am currently working with a system of 30 atoms of a organic molecule. I need to make a study related to determine the UV-Vis graphic as precisely as possible.
I am using DFT method. However, I am ...
- 10.7k
5
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130
views
Wade's rules applied to metallic elements
There are many examples of metallic clusters that distort from the structure predicted by Wade's rules to a more 'spherical', closo-like arrangement. For example,
$\ce{Bi8^2+}$ is a square antiprism ...
- 1,696
5
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108
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Advanced Quantum Chemistry Reference for Reactivity Phenomena
I'm currently in organic synthesis seeking to develop quantitative "physical" (that of a physicist), rather than "chemical", intuition for areas where traditional VSEPR/ MO models cannot fully ...
- 11.8k
5
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47
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Is there any molecule describable by three-level with mixed parity and transition dipole moments in different directions?
I would like to know if there are molecules described by a three-level system with mixed parity and transition dipole moments in different directions. By mixed parity I mean all three transitions can ...
- 155
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184
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Why isn't CASPT2 used in surface hopping simulations?
I will write what I think the answer is. I'd like someone to confirm and maybe explain in detail.
I think that since surface hopping dynamics simulates movements on PES, it has to calculate gradients ...
5
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0
answers
682
views
Difference of aggregate and cluster?
Can anyone tell me the difference of aggregates and clusters from the molecular point of view? Thank you so much.
CommunityBot
- 1
5
votes
1
answer
342
views
What are energies in computational methods relative to?
As per my understanding, in molecular mechanics (MM) the computed strain energy is based off the strain inherent in the molecule under study relative to an idealized form. For example, cyclobutane to ...
- 471
5
votes
1
answer
164
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How does one calculate chemical shift in a gauge independent manner?
The literature on ab initio calculations of chemical shift in NMR experiments usually provide Lamb's and Ramsey's formulae as the solution. Yet the expressions explicitly depend on vector potential ...
- 145
4
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44
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Helium ground state with Hartree–Fock using angular dependent functions
To compute the helium ground state (singlet) in Hartree–Fock theory we have to solve this equation:
$$ \left[ - \frac{\Delta}{2} - \frac{Z}{r} + \frac{1}{2} \int d^3 r' \frac{\vert \Psi(\boldsymbol{r'}...
- 38.4k