Questions tagged [configuration-interaction]

Questions to do with configuration interaction theory and applications.

Filter by
Sorted by
Tagged with
5 votes
0 answers
24 views

Core-valence separation (CVS) keyword in MRCC program [closed]

I am interested in using the CVS option in CI calculations to get core-excited states. I tried to use the MRCC program which possesses this option according to the manual (cvs=...). I performed some ...
EvGeniy's user avatar
  • 191
7 votes
1 answer
199 views

Start a CI calculation from HF/DFT chkfile in PySCF

I am trying to perform a CISD calculation in PySCF using the starting orbitals from an old DFT result. The DFT result was saved on a chkfile, mf.hdf5. The code that ...
David Sousa's user avatar
6 votes
1 answer
119 views

Has non-orthogonal CI (NOCI) been implemented in PySCF?

I'm kinda new to Pyscf and was wondering if there is a way to do non-orthogonal CI calculations with it. I would appreciate any help.
master_disaster's user avatar
3 votes
1 answer
84 views

Why is my CISD restart failing in PySCF?

A case that works In my answer to Restarting an FCI calculation in PySCF, I provided a folder full of input and output files that demonstrates saving (as a numpy ...
Nike Dattani's user avatar
  • 33.6k
3 votes
1 answer
156 views

Is PySCF able to print checkpoint files during a CISD calculation?

The problem I've described how to restart a CISD calculation in my answer to the question: Restarting an FCI calculation in PySCF, but this requires all iterations of the CISD calculation to finish, ...
Nike Dattani's user avatar
  • 33.6k
4 votes
2 answers
235 views

Which properties would you study to evaluate spatial confinement of a molecule

I'm modelling molecules confined within porous materials and I was wondering which molecular properties would you consider to access the confinement. Í'm thinking about looking into long-range ...
manuelpb's user avatar
  • 443
5 votes
1 answer
92 views

Finding the Configuration State Functions of Atoms

Is there a book or tabulated work where the configuration state functions of atoms have been documented? Just as useful would be information about computer programs that are able to predict the CSFs.
Severus Snape's user avatar
5 votes
1 answer
288 views

ORCA: CIS calculation for Helium atom

I want to understand ORCA output for CIS calculations. From the input file ...
Sergio's user avatar
  • 357
11 votes
2 answers
384 views

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 ...
user avatar
6 votes
1 answer
146 views

Transforming from CI basis to MO basis

Suppose, one knows the ground state wave function $|\Phi\rangle$ in terms of a slater determinant(SD) basis say, from a Configuration interaction calculation. $$|\Phi\rangle= c_{\text{HF}}\left|\Psi_{\...
user avatar
8 votes
1 answer
783 views

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, ...
S R Maiti's user avatar
  • 6,601
9 votes
1 answer
121 views

Which molecules have multi-reference character?

I'm using WebMO to construct molecules that have high multireference character, but I cannot seem to find any, or perhaps I'm not building them correctly on WebMO; I know singlet biradicals generally ...
MajesticMarkUp's user avatar
6 votes
1 answer
99 views

Accurate electron-hole localization for charge-transfer transitions

I'm studying the nature of electronic excitation in conjugated organic dyes. To define the donor and acceptor part I've run TDDFT and CIS calculation, they both gave similar set of configurations for ...
Roman's user avatar
  • 2,363
11 votes
3 answers
629 views

CCSD and CISD size-consistency problem

I have performed a Gaussian16 calculation to explore the size-consistency problem for the CISD method. The system I am studying is the water dimer and the results are not what I expected at first. I ...
Paul Logan's user avatar
8 votes
0 answers
108 views

How to classify ionic and covalent excited-states? [closed]

In spectroscopy it is common to describe excited-states as ionic or covalent. I understand the concept on a toy model e.g. $\ce{H2}$ with a minimal basis set \begin{align} \Phi_0 &= [\chi_A(1) + \...
Cody Aldaz's user avatar
  • 7,957
9 votes
1 answer
357 views

PySCF: eigenvalues, non-integer occupation, CISD calculations, and frozen lists

I have been performing CISD calculations with PySCF and I have a query surrounding the occupation of the orbitals. Here, the occupancies are calculated from the eigenvalues of the 1-electron ...
Wychh's user avatar
  • 2,015
5 votes
1 answer
203 views

What are the other matrix elements in singlet symmetry-adapted CISD?

Szabo/Ostlund list the CI matrix elements between singlet symmetry-adapted configurations (SAC) in Table 4.1 of their book: $$ \langle ^1\Psi^r_ a \lvert \mathcal{H} - E_ 0 \rvert ^1\Psi^r_ a \rangle, ...
TAR86's user avatar
  • 1,643
9 votes
1 answer
69 views

Extended Hybrid Methods

Hybrid DFT methods, where the functional is supplemented with Hartree-Fock exchange, have become increasingly popular due to their low cost and decent accuracy. Double hybrids, which mix in an MP2 ...
Tyberius's user avatar
  • 15.2k
10 votes
1 answer
98 views

Are there any programs that can do non-orthogonal CI?

Could you list any programs that can do non-orthogonal CI please?
Meilani Wibowo's user avatar
25 votes
2 answers
374 views

How to overcome the exponential wall encountered in full configurational interaction methods?

Similar to how a molecular orbital, also known as a 1-electron wavefunction, can be represented with a linear combination of “basis” functions, e.g., atomic orbitals (LCAO): $$\Phi(\mathbf{r})=\sum_i^...
Cody Aldaz's user avatar
  • 7,957