Unanswered Questions
310 questions with no upvoted or accepted answers
27
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How to calculate transition dipole moment from two known wavefunctions
I'm interested in calculating the transition dipole moment (TDM) from the information from two wavefunctions of different states. This is somewhat similar to calculating the molecular dipole moment ...
- 6,801
15
votes
0
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357
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Rotation around CC bond in 1,2-dioxetane: transition states and local minimum structures
TLDR:
What: Potential energy surface associated with rotation around CC bond in the ring-opened version of 1,2-dioxetane.
How: State average(4)-CASSCF(12,10)/VTZP constrained geometry optimizations ...
- 4,723
14
votes
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405
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What is the largest coupled cluster calculation that has ever been done (as of March 2019)?
I am doing some research and trying to make sure the numbers I am reporting are accurate.
I found that the paper by Sylvetsky et. al. says:[1]
We were, however, able to complete a ...
- 44.3k
13
votes
0
answers
365
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MNDO integrals in the global coordinate system
In MNDO and its descendants (Sewart's PMx models, Austin's AM1, MNDO/d, etc.), the nonvanishing two-center two-electron "coulomb integrals" are evaluated via a classical multipole expansion in a local ...
- 1
12
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309
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Accuracy of quantum chemistry calculations on iodine neglecting relativistic effects
Triiodothyronine is a molecule with three iodine atoms. If we attempted to calculate its properties with ab initio methods like Hartree-Fock or more complicated ab initio methods which included ...
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11
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Understanding two-electron integrals in Gaussian 09
I was comparing the two-electron integrals (electron repulsion integrals, ERI) printed by various well-established packages (Gaussian, GAMESS, Molpro etc.) and observed that Gaussian is the oddball in ...
- 9,881
10
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Which potentials are suitable for molecular dynamics simulation of simple explicit solvents?
Which potentials (force fields) are suitable for adequately simulating (mixtures of) explicit solvents? Interesting rheological properties include viscosity, surface tension, heat capacity.
- 4,265
9
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Vanishing integral rule for two-electron integrals
I understand the vanishing integral rule for a one-electron integral to be:
$$\langle i | \hat{O} | j \rangle = 0 \hspace{1cm} \mathrm{if} \hspace{0.2cm} \Gamma_O \neq \Gamma_i \otimes \Gamma_j$$
...
- 11.8k
9
votes
0
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258
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Quenching rates in nucleation MD simulations
I am trying to perform nucleation simulations with molecular dynamics. To prepare the metastable fluid, I am equilibrating at temperatures about 30 K above the melting temperature, and then "quenching"...
- 71.6k
9
votes
0
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898
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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 ...
- 3,405
9
votes
1
answer
246
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The Krieger-Li-Iafrate Approximation
I am having trouble understanding what KLI approximation is. Could someone explain it to me in an intuitive/simple way?
CommunityBot
- 1
8
votes
0
answers
124
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Are primitive GTOs normalised before contraction, or is the resultant basis function normalised afterwards?
I'm quite curious about this:
In a basis set (I'll just use minimal-basis STO-nG basis sets for convenience), the basis functions are written as a linear combination of primitive GTOs. Are the GTOs ...
CommunityBot
- 1
8
votes
0
answers
207
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Where is bifurcation situated on cyclohexane isomerisation PES?
I am wondering what does PES for cyclohexane isomerisation looks like.
I have two possibilities in mind but each has some kind of vagueness.
1) Starting from boat conformation minimum, followed by ...
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7
votes
0
answers
173
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Changing the level of theory for organometallic compounds
I'm finishing my Ph.D. in Inorganic Chemistry and having a debate with my supervisor. The work in question have two organometallic compounds A and B. The structures are based on X-Ray Diffraction, so ...
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7
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Additional example determining Marcus parameters searched
Background / theory: The electron transfer in organic materials was formalized by the Marcus theory, introducing $|H_{ab}|$ to describe the how molecules (or more generally: sites) are coupled with ...
- 30.4k