scholarly journals Vibrational heat-bath configuration interaction

2021 ◽  
Vol 154 (7) ◽  
pp. 074104
Author(s):  
Jonathan H. Fetherolf ◽  
Timothy C. Berkelbach
Keyword(s):  
Configuration Interaction ◽  
Heat Bath

scholarly journals Fast semistochastic heat-bath configuration interaction

2018 ◽  
Vol 149 (21) ◽  
pp. 214110 ◽  
Author(s):  
Junhao Li ◽  
Matthew Otten ◽  
Adam A. Holmes ◽  
Sandeep Sharma ◽  
C. J. Umrigar
Keyword(s):  
Configuration Interaction ◽  
Heat Bath

scholarly journals Stochastic Generalized Active Space Self-Consistent Field: Theory and Application

2021 ◽  
Author(s):  
Oskar Weser ◽  
Kai Guther ◽  
Khaldoon Ghanem ◽  
Giovanni Li Manni
Keyword(s):  
Wave Function ◽  
Configuration Interaction ◽  
Electron Correlation ◽  
Spin Exchange ◽  
Occupation Number ◽  
Heat Bath ◽  
Wave Functions ◽  
Density Matrices ◽  
Direct Evaluation ◽  
Active Space

An algorithm to perform stochastic generalized active space calculations, Stochastic-GAS, is presented, that uses the Slater determinant based FCIQMC algorithm as configuration interaction eigensolver. Stochastic-GAS allows the construction and stochastic optimization of preselected truncated configuration interaction wave functions, either to reduce the computational costs of large active space wave function optimizations, or to probe the role of specific electron correlation pathways. As for the conventional GAS procedure, the preselection of the truncated wave function is based on the selection of multiple active subspaces while imposing restrictions on the interspace excitations. Both local and cumulative minimum and maximum occupation number constraints are supported by Stochastic-GAS. The occupation number constraints are efficiently encoded in precomputed probability distributions, using the precomputed heat bath algorithm, which removes nearly all runtime overheads of GAS. This strategy effectively allows the FCIQMC dynamics to a priori exclude electronic configurations that are not allowed by GAS restrictions. Stochastic-GAS reduced density matrices are stochastically sampled, allowing orbital relaxations via Stochastic-GASSCF, and direct evaluation of properties that can be extracted from density matrices, such as the spin expectation value. Three test case applications have been chosen to demonstrate the flexibility of Stochastic-GAS: (a) the Stochastic-GASSCF optimization of a stack of five benzene molecules, that shows the applicability of Stochastic-GAS towards fragment-based chemical systems; (b) an uncontracted stochastic MRCISD calculation that correlates 96 electrons and 159 molecular orbitals, and uses a large (32, 34) active space reference wave function for an Fe(II)-porphyrin model system, showing how GAS can be applied to systematically recover dynamic electron correlation, and how in the specific case of the Fe(II)-porphyrin dynamic correlation further differentially stabilizes the triplet over the quintet spin state; (c) the study of an Fe4S4 cluster's spin-ladder energetics via highly truncated stochastic-GAS wave functions, where we show how GAS can be applied to understand the competing spin-exchange and charge-transfer correlating mechanisms in stabilizing different spin-states.

scholarly journals Excited States of Methylene, Polyenes, and Ozone from Heat-Bath Configuration Interaction

2018 ◽  
Vol 122 (10) ◽  
pp. 2714-2722 ◽  
Author(s):  
Alan D. Chien ◽  
Adam A. Holmes ◽  
Matthew Otten ◽  
C. J. Umrigar ◽  
Sandeep Sharma ◽  
...  
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Heat Bath

scholarly journals Excited states using semistochastic heat-bath configuration interaction

2017 ◽  
Vol 147 (16) ◽  
pp. 164111 ◽  
Author(s):  
Adam A. Holmes ◽  
C. J. Umrigar ◽  
Sandeep Sharma
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Heat Bath

scholarly journals Almost exact energies for the Gaussian-2 set with the semistochastic heat-bath configuration interaction method

2020 ◽  
Vol 153 (12) ◽  
pp. 124117 ◽  
Author(s):  
Yuan Yao ◽  
Emmanuel Giner ◽  
Junhao Li ◽  
Julien Toulouse ◽  
C. J. Umrigar
Keyword(s):  
Configuration Interaction ◽  
Heat Bath ◽  
Interaction Method ◽  
Configuration Interaction Method
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