All Questions
Tagged with quantum-chemistry theoretical-chemistry
194
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Why Car Parrinello Molecular Dynamics doesn't need an SCF calculation at every time-step?
Reading the various terms of the Lagrangian in CP-MD I'm trying to understand why there is not an SCF procedure hidden there.
In fact, it seems to me like the second term of the Eulero-Lagrange ...
- 101
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38
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Resonance stabilization : lowering of kinetic energy or electron repulsion?
Resonance stabilization, or delocalization stabilization, occurs when the overall energy of the molecule is lowered compared the localized "resonance structures".
In solid state physics, or ...
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36
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How to find the global minima of a supramolecular complex in computational chemistry?
So this is more of a complex problem, and my masters thesis could greatly benefit if I find an answer to this.
Essentially, I have a supramolecular inclusion complex. There is this molecule A (the ...
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98
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Doubt on vibronic transitions
When we justify the presence of electronic transitions forbidden by Laporte selection rule, the coupling between electronic and vibrational states help us. Why we say that in this way we are ...
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Are there examples of publications using DFT instead of HF as a coupled-cluster reference?
I have been searching for a while, and only managed to find an article by M. Saitow,[1] where CAM-B3LYP orbitals are used. I was wondering if this has been done elsewhere.
It was recommended to me by ...
- 61
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53
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Spin-preserving excitations
I'm currently working on quantum chemistry with quantum machine learning and one of the operations considered for the calculation is the excitation (and desexcitation) of an electron from an orbital ...
- 39
2
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1
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267
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Is there a difference between Hartree-Fock method and LCAO?
I have to dive in some quantum chemistry for a quantum machine learning project and I came across the so-called Hartree-Fock method.
In one of the reference I used, they considered electrons as ...
- 39
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25
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Rationalisation of stabilising dispersion interactions in HgS via QM
It is well-known that mercury(II) sulfide, HgS, is extremely inert- for example, it has one of the lowest solubilities of nearly all known compounds in water(check Wikipedia). There are two well-known ...
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275
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Provide a mathematical explanation of why the non-relativistic Schrödinger equation for a Molecular system, cannot be solved analytically?
The non-relativistic Schrödinger Equation is:
$\widehat{H}|\psi\rangle=E|\psi\rangle$
Where $\widehat{H}$ is the Molecular Hamiltonian in Atomic Units and has the following terms:
$$ \widehat{H}
=...
- 49
4
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1
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223
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How is a Barrierless Reaction Confirmed in Quantum Chemistry?
Background:
Some quantum chemistry papers explore potential energy surfaces by characterizing critical points with an ab initio method. Reactants, products, intermediates, and transition states are ...
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129
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How to calculate <ab|ab> integrals to carry out Schwarz pre-screening of molecular integrals
During writing my own two-electron integration library I faced an issue of dealing with integrals that have very small values beyond the C/C++ double data type. ...
3
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101
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What is the physical significance of the damping function in calculation of vdW interaction energy?
In order to take care for the singularity (also removing the double counting of exchange-correlation) obtained with this expression,
$$E_\mathrm{vdW} = \frac{C^6}{R^6}$$
many type of damping functions ...
- 181
7
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1
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267
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Variational (Rayleigh-Ritz) method and multielectron wavefunction
I am studying Rayleigh-Ritz method and I have some problem to understand what the final wavefunction looks like. Suppose that we have a system with $N$ electrons, atom or molecule. We are interested ...
- 766
3
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85
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State-of-the-art results on molecular vibronic energy calculation
Could someone kindly point me to the latest records in scale, accuracy, or timescale for molecular vibronic energy calculation?
I tried to start with Google Scholar: https://scholar.google.com/scholar?...
- 245
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Schrodinger operator with matrix potential and Green's function
Clearly Schrodinger operators with matrix potentials appear very naturally in molecular dynamics/quantum chemistry, particularly when considering a crude adiabatic basis or diabatic basis for an ...
