Further Development of iCIPT2 for Strongly Correlated Electrons

Ning Zhang; Wenjian Liu; Mark R Hoffmann

doi:10.1021/acs.jctc.0c01187

Further Development of iCIPT2 for Strongly Correlated Electrons

J Chem Theory Comput. 2021 Feb 9;17(2):949-964. doi: 10.1021/acs.jctc.0c01187. Epub 2021 Jan 7.

Authors

Ning Zhang¹, Wenjian Liu², Mark R Hoffmann³

Affiliations

¹ Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
² Qingdao Institute for Theoretical and Computational Sciences, Shandong University, Qingdao, Shandong 266237, China.
³ Chemistry Department, University of North Dakota, Grand Forks, North Dakota 58202-9024, United States.

PMID: 33410692
DOI: 10.1021/acs.jctc.0c01187

Abstract

The efficiency of the recently proposed iCIPT2 [iterative configuration interaction (iCI) with selection and second-order perturbation theory (PT2); J. Chem. Theory Comput. 2020, 16, 2296] for strongly correlated electrons is further enhanced (by up to 20×) by using (1) a new ranking criterion for configuration selection, (2) a new particle-hole algorithm for Hamiltonian construction over randomly selected configuration state functions (CSF), and (3) a new data structure for the quick sorting of the variational and first-order interaction spaces. Meanwhile, the memory requirement is also significantly reduced. As a result, this improved implementation of iCIPT2 can handle 1 order of magnitude more CSFs than the previous version, as revealed by taking the chromium dimer and an iron-sulfur cluster, [Fe₂S₂(SCH₃)]₄^2-, as examples.