Questions tagged [ab-initio]

For questions relating to quantum chemistry using wavefunction-based methods and solving the Schrödinger equation.

8 questions with no upvoted or accepted answers
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How to evaluate the expectation value of the Hamiltonian for a three electron Slater determinant?

I'm having trouble with a few concepts dealing with slater determinants and many electron systems. In particular, when dealing with 3 electron systems, I know that $$ \psi_0 = \frac{1}{\sqrt{6}} \det ...
5
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0answers
51 views

Paper Data Replication

I read a paper recently - Here. I found the concept of Electride materials very interesting and wanted to mess around with them myself. I tried to replicate the partial electron density plots shown in ...
5
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1answer
135 views

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 ...
3
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0answers
66 views

Bond order analysis in molpro

I'm trying to compute bond orders in a molecule, let's consider S2 as an example. I'm not entirely sure what's the right way to do that, but I assume NBO (Natural Bond Orbital) should give me what I ...
2
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0answers
29 views

tolerable error, CASSCF simulation of UV/Vis spectrum

Please forgive my ignorance of experimental spectroscopy. I am a computational chemist, not an experimental one. My question is: what would be considered a tolerable or reasonable difference between ...
2
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0answers
26 views

GVP(PP) orbital energies?

Hartree-Fock orbital energies can be interpreted physically, e.g. in Koopmans theorem, while one cannot assign active MCSCF orbitals to energies in general. What about GVB, say for example GVB(PP) ...
2
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0answers
45 views

Can someone suggest me important references for deriving EOM in MCSCF?

I am currently starting a project dealing with MCSCF method. Can someone please give me references (papers or lecture notes are preferred) which may be considered as the "corner stones" in the history ...
0
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0answers
28 views

How to use potential energy surface represented by a neural network for molecular dynamics simulation?

I trained a neural network that represents the potential energy surface of a periodic system consists of $50$ atoms. The neural network takes the structure proposed by Behler and Parrinello in 2007. ...