# Internally contracted multiconfiguration-reference configuration interaction calculations for excited states

@article{Knowles1992InternallyCM, title={Internally contracted multiconfiguration-reference configuration interaction calculations for excited states}, author={Peter J. Knowles and Hans-Joachim Werner}, journal={Theoretica chimica acta}, year={1992}, volume={84}, pages={95-103} }

SummaryThe calculation of electronically excited states with the internally contracted multiconfiguration-reference configuration interaction (CMRCI) method is discussed. A straightforward method, in which contracted functions for all states are included in the basis, is shown to be very accurate and stable even in cases of narrow avoided crossings. However, the expense strongly increases with the number of states. A new method is proposed, which employs different contracted basis sets for each… Expand

#### 377 Citations

Calculation of transition moments between internally contracted MRCI wave functions with non-orthogonal orbitals

- Chemistry
- 2007

We present an efficient algorithm for calculating transition properties between internally contracted multireference configuration interaction (MRCI) wave functions using different orbitals for both… Expand

Multireference configuration interaction treatment of excited-state electron correlation in periodic systems: the band structure of trans-polyacetylene

- Chemistry, Physics
- 2004

A systematic method to account for electron correlation in periodic systems which can predict quantitatively correct band structures of non-conducting solids from first principles is presented. Using… Expand

New schemes for internally contracted multi-reference configuration interaction.

- Physics, Medicine
- The Journal of chemical physics
- 2014

This work presents a new internally contracted multi-reference configuration interaction (MRCI) scheme by applying the graphical unitary group approach and the hole-particle symmetry, which greatly simplifies calculations of coupling coefficients and CI matrix elements. Expand

Comparison of fully internally and strongly contracted multireference configuration interaction procedures.

- Chemistry, Medicine
- The Journal of chemical physics
- 2016

The results indicate that the SC-scheme, which is successful in the context of second- and third-order perturbation theory, does not offer computational advantages and at the same time leads to much larger errors than the PC and FIC schemes. Expand

Explicitly correlated multireference configuration interaction with multiple reference functions: avoided crossings and conical intersections.

- Chemistry, Medicine
- The Journal of chemical physics
- 2011

An explicitly correlated multireference configuration interaction method (MRCI-F12) with multiple reference functions that can be routinely applied to nearly degenerate molecular electronic structures near conical intersections and avoided crossings and introduces a singles correction to the CASSCF reference energies, applicable to multi-state calculations. Expand

A new internally contracted multi-reference configuration interaction method.

- Chemistry, Medicine
- The Journal of chemical physics
- 2011

We present a new internally contracted multi-reference configuration interaction (MRCI) method which, at the same time, efficiently handles large active orbital spaces, long configuration expansions,… Expand

Explicitly correlated multireference configuration interaction: MRCI-F12.

- Chemistry, Medicine
- The Journal of chemical physics
- 2011

An internally contracted multireference configuration interaction is developed which employs wave functions that explicitly depend on the electron-electron distance (MRCI-F12). This MRCI-F12 method… Expand

Communication: extended multi-state complete active space second-order perturbation theory: energy and nuclear gradients.

- Physics, Medicine
- The Journal of chemical physics
- 2011

The extended multireference quasi-degenerate perturbation theory, proposed by Granovsky, is combined with internally contracted multi-state complete active space second-order perturbations theory (XMS-CASPT2) and guarantees invariance of the theory with respect to unitary rotations of the reference functions. Expand

The multiconfigurational-reference internally contracted configuration interaction/complete basis set study of the excited states of the trifluoride anion F3(-).

- Chemistry, Medicine
- The Journal of chemical physics
- 2008

The multiconfigurational-reference internally contracted configuration interaction (MRCI)/aug-cc-pVQZ-based computational protocol was employed to search for the minima of the potential energy… Expand

Combining Internally Contracted States and Matrix Product States To Perform Multireference Perturbation Theory.

- Mathematics, Medicine
- Journal of chemical theory and computation
- 2017

We present two efficient and intruder-free methods for treating dynamic correlation on top of general multiconfiguration reference wave functions - including such as obtained by the density matrix… Expand

#### References

SHOWING 1-10 OF 17 REFERENCES

An efficient internally contracted multiconfiguration–reference configuration interaction method

- Chemistry
- 1988

A new internally contracted direct multiconfiguration–reference configuration interaction (MRCI) method is described which allows the use of much larger reference spaces than any previous MRCI… Expand

A comparison of variational and non-variational internally contracted multiconfiguration-reference configuration interaction calculations

- Chemistry
- 1990

SummaryThe internally contracted multiconfiguration-reference configuration interaction (CMRCI) method and several non-variational variants of this method (averaged coupled pair approximation (ACPF),… Expand

The CASSCF state interaction method

- Chemistry
- 1989

Abstract A method is described to calculate the matrix elements of one- and two-electron operators for CASSCF wavefunctions employing individually optimized orbitals. The computation procedure is… Expand

The self‐consistent electron pairs method for multiconfiguration reference state functions

- Chemistry
- 1982

An efficient direct CI method which includes all singly and doubly substituted configurations with respect to an arbitrary multiconfiguration (MCSCF) reference function is described. The… Expand

Accurate multireference configuration interaction calculations of the potential energy function and the dissociation energy of N2

- Chemistry
- 1991

The potential energy function of the N2 molecule is calculated using the internally contracted multireference CI method (CMRCI) and complete active space SCF (CASSCF) reference wave functions. A full… Expand

Direct configuration interaction with a reference state composed of many reference configurations

- Physics
- 1980

The configuration interaction method where a single reference state is composed of a linear combination of reference configurations is analyzed in detail. In this method single and double… Expand

An efficient method for the evaluation of coupling coefficients in configuration interaction calculations

- Chemistry
- 1988

Abstract A new method for evaluating one-particle coupling coefficients in a general configuration interaction calculation is presented. Through repeated application and use of resolutions of the… Expand

Individualized configuration selection in CI calculations with subsequent energy extrapolation

- Physics
- 1974

A configuration selection method for CI calculations is discussed and applied in which the energy lowering produced in a secular equation by the addition of a given test species to a series of… Expand

Advanced theories and computational approaches to the electronic structure of molecules

- Chemistry
- 1984

Chemical Computations on an Attached Processor: Quantum Chemistry Applications.- Considerations in Vectorizing the CI Procedure.- The Method of Self Consistent Electron Pairs. A Matrix Oriented… Expand

The shape‐driven graphical unitary group approach to the electron correlation problem. Application to the ethylene molecule

- Chemistry
- 1982

A new method for the approximate solution of Schrodinger’s equation for many electron molecular systems is outlined. The new method is based on the unitary group approach (UGA) and exploits in… Expand