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Analytical derivatives of the individual state energies in ensemble density functional theory method. I. General formalism

Authors :
Michael Filatov
Fang Liu
Todd J. Martínez
Source :
The Journal of Chemical Physics. 147:034113
Publication Year :
2017
Publisher :
AIP Publishing, 2017.

Abstract

The state-averaged (SA) spin restricted ensemble referenced Kohn-Sham (REKS) method and its state interaction (SI) extension, SI-SA-REKS, enable one to describe correctly the shape of the ground and excited potential energy surfaces of molecules undergoing bond breaking/bond formation reactions including features such as conical intersections crucial for theoretical modeling of non-adiabatic reactions. Until recently, application of the SA-REKS and SI-SA-REKS methods to modeling the dynamics of such reactions was obstructed due to the lack of the analytical energy derivatives. In this work, the analytical derivatives of the individual SA-REKS and SI-SA-REKS energies are derived. The final analytic gradient expressions are formulated entirely in terms of traces of matrix products and are presented in the form convenient for implementation in the traditional quantum chemical codes employing basis set expansions of the molecular orbitals. The implementation and benchmarking of the derived formalism will be described in a subsequent article of this series.

Details

ISSN :
10897690 and 00219606
Volume :
147
Database :
OpenAIRE
Journal :
The Journal of Chemical Physics
Accession number :
edsair.doi.dedup.....ea741b3b22d2fa637e121bc3b0aca965
Full Text :
https://doi.org/10.1063/1.4994542