Diabatic-At-Construction Method for Diabatic and Adiabatic Ground and Excited States Based on Multistate Density Functional Theory

Adam Grofe, Zexing Qu, Donald G. Truhlar, Hui Li, Jiali Gao

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29 Scopus citations

Abstract

We describe a diabatic-at-construction (DAC) strategy for defining diabatic states to determine the adiabatic ground and excited electronic states and their potential energy surfaces using the multistate density functional theory (MSDFT). The DAC approach differs in two fundamental ways from the adiabatic-to-diabatic (ATD) procedures that transform a set of preselected adiabatic electronic states to a new representation. (1) The DAC states are defined in the first computation step to form an active space, whose configuration interaction produces the adiabatic ground and excited states in the second step of MSDFT. Thus, they do not result from a similarity transformation of the adiabatic states as in the ATD procedure; they are the basis for producing the adiabatic states. The appropriateness and completeness of the DAC active space can be validated by comparison with experimental observables of the ground and excited states. (2) The DAC diabatic states are defined using the valence bond characters of the asymptotic dissociation limits of the adiabatic states of interest, and they are strictly maintained at all molecular geometries. Consequently, DAC diabatic states have specific and well-defined physical and chemical meanings that can be used for understanding the nature of the adiabatic states and their energetic components. Here we present results for the four lowest singlet states of LiH and compare them to a well-tested ATD diabatization method, namely the 3-fold way; the comparison reveals both similarities and differences between the ATD diabatic states and the orthogonalized DAC diabatic states. Furthermore, MSDFT can provide a quantitative description of the ground and excited states for LiH with multiple strongly and weakly avoided curve crossings spanning over 10 Å of interatomic separation.

Original languageEnglish (US)
Pages (from-to)1176-1187
Number of pages12
JournalJournal of Chemical Theory and Computation
Volume13
Issue number3
DOIs
StatePublished - Mar 14 2017

Bibliographical note

Funding Information:
The work was supported in part by grants from the National Natural Science Foundation of China (Grant Number 91541124) and the National Institutes of Health (GM46736) to J.G. and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0015997 (D.G.T.).

Publisher Copyright:
© 2017 American Chemical Society.

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