Questions tagged [many-body-perturbation-theory]
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9
questions
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What does it mean when the first order correction energy is 0?
Suppose I have the following Hamiltonian to start
$$ H_0 = \begin{pmatrix} 0 & 0 & 0 & 0\\ 0 & 0 & 2 & 0\\ 0 & 2 & 0 & 0\\ 0 & 0 & 0 & 0 \end{pmatrix} $$...
- 307
8
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1
answer
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What do size-extensivity and size-consistency mean?
I have heard both terms in various lectures and books on quantum chemistry, however, I have not found a proper explanation of them. As I understand now, size consistency of a method means for example, ...
- 5,499
7
votes
1
answer
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How does coupled cluster doubles (CCD) compare to MP2?
I have seen an increase in the use of the coupled-cluster doubles (CCD) method recently. CCD uses the exponential ansatz of the coupled cluster equations, but only includes amplitudes to double ...
- 2,431
7
votes
1
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What are the types of PT applied to electronic structure methods?
The motivation for this question is similar in nature to the series of questions on different methods :
What are the types of SCF?
What are the types of MCSCF?
What are the types of Quantum Monte ...
- 905
7
votes
2
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Geometry optimization with Moller-Plesset MP4
Can we optimize a molecular structure using Moller-Plesset MP4 method on GAUSSIAN software? If yes what keyword do we have to add?
- 527
11
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2
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DFT functionals from MP2 methods
I have heard people talk about DFT functionals built starting from MP2 corrections. Do you happen to have a reference I read about that from?
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15
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3
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How should I compare different basis sets for post-Hartree-Fock methods?
HF or DFT methods are variational so I can confidently say that any basis set that gives the lowest energy is the best for that system. However, I have learnt that post-HF methods such as MP2, MP3, ...
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14
votes
1
answer
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Why are single excitations ignored in the MP2 component of double hybrid functional calculations?
In the original paper by Grimme introducing double hybrid functionals (also summarized in just 3 paragraphs here), it says:
"[As] opposed to nonempirical versions of KS-PT2 [19],
the single ...
- 27.8k
8
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The correlation energy from frozen natural orbtials (FNOs) using CCSD and MPBT(2)?
In other works and from the paper: Scaling Up Electronic Structure Calculations on Quantum Computers: The Frozen Natural Orbital Based Method of Increments.
I have seen that the corrected CCSD ...
- 1,789