Full Correlation in a Multiconfigurational Study of Bimetallic Clusters

Restricted Active Space Pair-Density Functional Theory Study of [2Fe-2S] Systems

Davide Presti, Samuel Stoneburner, Donald G Truhlar, Laura Gagliardi

Research output: Contribution to journalArticle

Abstract

Iron-sulfur clusters play a variety of important roles in protein chemistry, and understanding the energetics of their spin ladders is an important part of understanding these roles. Computational modeling can offer considerable insights into such problems; however, calculations performed thus far on systems with multiple transition metals have typically either been restricted to a single-configuration representation of the density, as in Kohn-Sham theory, or been limited to correlating excitations only within an active space, as in active-space self-consistent field methods. For greater reliability, a calculation should include full correlation, that is, not only correlation internal to the active space but also external correlation, and it is desirable to combine this full-electron correlation with a multiconfigurational representation of the wave function, but this has been impractical thus far. Here, we present an affordable way to do this by using restricted active-space pair-density functional theory. We show that with this method, it is possible to compute the entire spin ladder for systems containing two Fe centers bridged by two S atoms. On the other hand, with second-order perturbation theory, only the high-spin states can be computed. A key result is that, in agreement with some experiments, we find a high-spin ground state for a relaxed reduced [Fe2S2(SCH3)4]3- cluster, which is a novel result in computational studies.

Original languageEnglish (US)
Pages (from-to)11899-11907
Number of pages9
JournalJournal of Physical Chemistry C
Volume123
Issue number18
DOIs
StatePublished - May 9 2019

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Ladders
Density functional theory
density functional theory
Electron correlations
Wave functions
Sulfur
ladders
Ground state
Transition metals
Iron
Proteins
Atoms
self consistent fields
sulfur
perturbation theory
Experiments
transition metals
wave functions
chemistry
proteins

Cite this

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title = "Full Correlation in a Multiconfigurational Study of Bimetallic Clusters: Restricted Active Space Pair-Density Functional Theory Study of [2Fe-2S] Systems",
abstract = "Iron-sulfur clusters play a variety of important roles in protein chemistry, and understanding the energetics of their spin ladders is an important part of understanding these roles. Computational modeling can offer considerable insights into such problems; however, calculations performed thus far on systems with multiple transition metals have typically either been restricted to a single-configuration representation of the density, as in Kohn-Sham theory, or been limited to correlating excitations only within an active space, as in active-space self-consistent field methods. For greater reliability, a calculation should include full correlation, that is, not only correlation internal to the active space but also external correlation, and it is desirable to combine this full-electron correlation with a multiconfigurational representation of the wave function, but this has been impractical thus far. Here, we present an affordable way to do this by using restricted active-space pair-density functional theory. We show that with this method, it is possible to compute the entire spin ladder for systems containing two Fe centers bridged by two S atoms. On the other hand, with second-order perturbation theory, only the high-spin states can be computed. A key result is that, in agreement with some experiments, we find a high-spin ground state for a relaxed reduced [Fe2S2(SCH3)4]3- cluster, which is a novel result in computational studies.",
author = "Davide Presti and Samuel Stoneburner and Truhlar, {Donald G} and Laura Gagliardi",
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language = "English (US)",
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T1 - Full Correlation in a Multiconfigurational Study of Bimetallic Clusters

T2 - Restricted Active Space Pair-Density Functional Theory Study of [2Fe-2S] Systems

AU - Presti, Davide

AU - Stoneburner, Samuel

AU - Truhlar, Donald G

AU - Gagliardi, Laura

PY - 2019/5/9

Y1 - 2019/5/9

N2 - Iron-sulfur clusters play a variety of important roles in protein chemistry, and understanding the energetics of their spin ladders is an important part of understanding these roles. Computational modeling can offer considerable insights into such problems; however, calculations performed thus far on systems with multiple transition metals have typically either been restricted to a single-configuration representation of the density, as in Kohn-Sham theory, or been limited to correlating excitations only within an active space, as in active-space self-consistent field methods. For greater reliability, a calculation should include full correlation, that is, not only correlation internal to the active space but also external correlation, and it is desirable to combine this full-electron correlation with a multiconfigurational representation of the wave function, but this has been impractical thus far. Here, we present an affordable way to do this by using restricted active-space pair-density functional theory. We show that with this method, it is possible to compute the entire spin ladder for systems containing two Fe centers bridged by two S atoms. On the other hand, with second-order perturbation theory, only the high-spin states can be computed. A key result is that, in agreement with some experiments, we find a high-spin ground state for a relaxed reduced [Fe2S2(SCH3)4]3- cluster, which is a novel result in computational studies.

AB - Iron-sulfur clusters play a variety of important roles in protein chemistry, and understanding the energetics of their spin ladders is an important part of understanding these roles. Computational modeling can offer considerable insights into such problems; however, calculations performed thus far on systems with multiple transition metals have typically either been restricted to a single-configuration representation of the density, as in Kohn-Sham theory, or been limited to correlating excitations only within an active space, as in active-space self-consistent field methods. For greater reliability, a calculation should include full correlation, that is, not only correlation internal to the active space but also external correlation, and it is desirable to combine this full-electron correlation with a multiconfigurational representation of the wave function, but this has been impractical thus far. Here, we present an affordable way to do this by using restricted active-space pair-density functional theory. We show that with this method, it is possible to compute the entire spin ladder for systems containing two Fe centers bridged by two S atoms. On the other hand, with second-order perturbation theory, only the high-spin states can be computed. A key result is that, in agreement with some experiments, we find a high-spin ground state for a relaxed reduced [Fe2S2(SCH3)4]3- cluster, which is a novel result in computational studies.

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