2020/10/19 by Robert J. Anderson, George H. Booth, Anderson, Robert J. +1
Materials Science · Physics and Astronomy · #Advanced Chemical Physics Studies #Catalytic Processes in Materials Science #Chemical Physics (physics.chem-ph) #Computational Physics (physics.comp-ph) #FOS: Physical sciences #Magnetism in coordination complexes #Strongly Correlated Electrons (cond-mat.str-el)
paper · pdf · doi:10.48550/arxiv.2010.09558
openalex publication_date 2020/10/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
An adaptation of the full configuration interaction quantum Monte Carlo\n(FCIQMC) method is presented, for correlated electron problems containing heavy\nelements and the presence of significant relativistic effects. The modified\nalgorithm allows for the sampling of the four-component spinors of the\nDirac--Coulomb(--Breit) Hamiltonian within the relativistic no-pair\napproximation. The loss of spin symmetry and the general requirement for\ncomplex-valued Hamiltonian matrix elements are the most immediate\nconsiderations in expanding the scope of FCIQMC into the relativistic domain,\nand the alternatives for their efficient implementation are motivated and\ndemonstrated. For the canonical correlated four-component chemical benchmark\napplication of Thallium Hydride, we show that the necessary modifications do\nnot particularly adversely affect the convergence of the systematic (initiator)\nerror to the exact correlation energy for FCIQMC calculations, which is\nprimarily dictated by the sparsity of the wave function, allowing the\ncomputational effort to somewhat bypass the formal increases in Hilbert space\ndimension for these problems. We apply the method to the larger problem of the\nspectroscopic constants of Tin Oxide, correlating 28 electrons in 122\nKramers-paired spinors, finding good agreement with experimental and prior\ntheoretical relativistic studies.\n