Multi-State Formulation of the Frozen-Density Embedding Quasi-Diabatization Approach

TL;DR

This paper introduces a multi-state extension of the FDE-diab methodology, allowing efficient calculation of spin-density distributions and excitation energies in large molecular systems, with approximations that reduce computational cost.

Contribution

The paper develops a multi-state implementation of FDE-diab, enabling coupled charge-localized states calculations for ground and excited states, with cost-effective approximations.

Findings

Results comparable to high-level wave function methods

New approximate schemes reduce computational effort

Method applicable to large biochemical systems

Abstract

We present a multi-state implementation of the recently developed FDE-diab methodology [J. Chem. Phys., 148 (2018), 214104] in the Serenity program. The new framework extends the original approach such that any number of charge-localized quasi-diabatic states can be coupled, giving an access to calculations of ground and excited state spin-density distributions as well as to excitation energies. We show that it is possible to obtain results similar to those from correlated wave function approaches such as the complete active space self-consistent field method at much lower computational effort. Additionally, we present a series of approximate computational schemes, which further decrease the overall computational cost and systematically converge to the full FDE-diab solution. The proposed methodology enables computational studies on spin-density distributions and related properties for large molecular systems of biochemical interest.