Questions tagged [full-configuration-interaction]

For questions about FCI (full configuration interaction) calculations.

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Question on possible cancellations in the computation of Dyson orbitals from FCC/FCI wavefunctions [closed]

Dyson orbitals are mathematically meaningful, in the sense that they, unlike the DFT orbitals for instance, are actual observables of the wavefunction, instead of being "the other way around"...
1 vote
0 answers

Question on known expression (see post) of exact XC functional in analytic (but not closed) form

This paper analytically solves the "inverse DFT problem" of mapping the ground-state density to the exact XC functional. And the exact density, i.e. the FCC/FCI density, can be expressed as ...
4 votes
2 answers

Restarting an FCI calculation in PySCF

My question is, if there is a way to continue an earlier FCI calculation in PySCF. Imagine you initially just need energies converged up to a certain threshold: ...
6 votes
2 answers

What are the limitations of FCI?

I am aware of the fact that Full Configuration Interaction scales poorly. Taking into account that the number of $n$-times excited Slater determinants of an $N$-particle System with $M$ basis ...
11 votes
2 answers

FCI without Hartree-Fock

Recently, I came across some lecture notes on electronic structure theory which had something peculiar about it. I noticed that FCI (configuration interaction) was introduced before Hartree-Fock ...
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7 votes
3 answers

Open source FCI solvers for exact diagonalization of the many-electron Hamiltonian

What open source solvers (according to the generally accepted Open Source Definition i.e. licensed under a valid open source license) are available for full configuration interaction calculations? ...
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9 votes
3 answers

What are the advantages of the Davidson diagonalization method over other sparse matrix diagonalization methods?

I am interested to understand the advantages of the Davidson diagonalization method over other sparse matrix diagonalization routines. For instance, Intel MKL.
  • 1,869
6 votes
2 answers

Analytic Hessian at the level of full CI?

This is a follow-up question to my previous question: Computing analytic derivatives of molecular Hamiltonians obtained from solving Hartree-Fock equations. After looking at various quantum chemistry ...
8 votes
1 answer

What do the parameters at the top of an FCIDUMP file mean?

A while ago I wrote a simple program that takes in an FCIDUMP file (generated by MOLRPO) and can determine matrix elements (or ...
  • 731
10 votes
1 answer

How to calculate FCI matrix elements from an FCIDUMP file

I'm interested in writing a simple program (as an exercise) that takes an FCIDUMP file (e.g. from a Molpro calculation) and can determine FCI matrix elements (e.g. to construct the entire FCI matrix ...
  • 731
14 votes
1 answer

Orbitals in full CI and DFT with true functional

Is there any paper that proves/disproves that the occupied orbitals obtained using full Configuration Interaction (CI) are the same as the orbitals obtained using DFT (assuming we use the exact ...
  • 883
28 votes
1 answer

How accurate are the most accurate calculations?

Taking into account the fact that the theory of quantum gravity does not exist and the QED calculations are not possible for most realistic chemical systems, what levels of accuracy can we expect from ...
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