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Title: Nonadiabatic Excited-State Molecular Dynamics for Open-Shell Systems

Abstract

Nonadiabatic Molecular Dynamics (NAMD) of excited states has been widely used in the simulation of photoinduced phenomena. However, the inability to treat bond breaking and forming processes with single-reference electronic structure methods limits their application in photochemistry for extended molecular systems. In this work, the extension of excited-state NAMD for open-shell systems is developed and implemented in the NEXMD software. We present the spin-unrestricted CIS and TDSCF formalism for the ground and excited states, analytical derivatives, and nonadiabatic derivative couplings for the respective potential energy surfaces. Next, this methodology is employed to study the photochemical reaction of three model molecules. The results demonstrate the advantage of the open-shell approach in modeling photochemical reactions, especially involving bond breaking processes. We find that the open-shell method lowers the reaction barrier at the bond-breaking limits resulting in larger calculated photochemical quantum yields compared to the respective closed-shell results. We also address problems related to spin contamination in the open-shell method, especially when molecular geometries are far from equilibrium.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Southern California, Los Angeles, CA (United States)
Publication Date:
Research Org.:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States). Center for Integrated Nanotechnologies (CINT)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1614840
Report Number(s):
LA-UR-19-29917
Journal ID: ISSN 1549-9618
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Chemical Theory and Computation
Additional Journal Information:
Journal Volume: 16; Journal Issue: 4; Journal ID: ISSN 1549-9618
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; Inorganic and physical chemistry; Material science; Contamination; Energy; Quantum mechanics; Computational chemistry; Excited states

Citation Formats

Zhang, Yu, Li, Linqiu, Tretiak, Sergei, and Nelson, Tammie Renee. Nonadiabatic Excited-State Molecular Dynamics for Open-Shell Systems. United States: N. p., 2020. Web. doi:10.1021/acs.jctc.9b00928.
Zhang, Yu, Li, Linqiu, Tretiak, Sergei, & Nelson, Tammie Renee. Nonadiabatic Excited-State Molecular Dynamics for Open-Shell Systems. United States. doi:10.1021/acs.jctc.9b00928.
Zhang, Yu, Li, Linqiu, Tretiak, Sergei, and Nelson, Tammie Renee. Mon . "Nonadiabatic Excited-State Molecular Dynamics for Open-Shell Systems". United States. doi:10.1021/acs.jctc.9b00928.
@article{osti_1614840,
title = {Nonadiabatic Excited-State Molecular Dynamics for Open-Shell Systems},
author = {Zhang, Yu and Li, Linqiu and Tretiak, Sergei and Nelson, Tammie Renee},
abstractNote = {Nonadiabatic Molecular Dynamics (NAMD) of excited states has been widely used in the simulation of photoinduced phenomena. However, the inability to treat bond breaking and forming processes with single-reference electronic structure methods limits their application in photochemistry for extended molecular systems. In this work, the extension of excited-state NAMD for open-shell systems is developed and implemented in the NEXMD software. We present the spin-unrestricted CIS and TDSCF formalism for the ground and excited states, analytical derivatives, and nonadiabatic derivative couplings for the respective potential energy surfaces. Next, this methodology is employed to study the photochemical reaction of three model molecules. The results demonstrate the advantage of the open-shell approach in modeling photochemical reactions, especially involving bond breaking processes. We find that the open-shell method lowers the reaction barrier at the bond-breaking limits resulting in larger calculated photochemical quantum yields compared to the respective closed-shell results. We also address problems related to spin contamination in the open-shell method, especially when molecular geometries are far from equilibrium.},
doi = {10.1021/acs.jctc.9b00928},
journal = {Journal of Chemical Theory and Computation},
issn = {1549-9618},
number = 4,
volume = 16,
place = {United States},
year = {2020},
month = {3}
}

Journal Article:
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