Improved Fast Randomized Iteration Approach to Full Configuration Interaction

Samuel M. Greene, Robert J. Webber, Jonathan Weare, Timothy C. Berkelbach

Research output: Contribution to journalArticlepeer-review


We present three modifications to our recently introduced fast randomized iteration method for full configuration interaction (FCI-FRI) and investigate their effects on the method's performance for Ne, H2O, and N2. The initiator approximation, originally developed for full configuration interaction quantum Monte Carlo, significantly reduces statistical error in FCI-FRI when few samples are used in compression operations, enabling its application to larger chemical systems. The semistochastic extension, which involves exactly preserving a fixed subset of elements in each compression, improves statistical efficiency in some cases but reduces it in others. We also developed a new approach to sampling excitations that yields consistent improvements in statistical efficiency and reductions in computational cost. We discuss possible strategies based on our findings for improving the performance of stochastic quantum chemistry methods more generally.

Original languageEnglish (US)
Pages (from-to)5572-5585
Number of pages14
JournalJournal of chemical theory and computation
Issue number9
StatePublished - Sep 8 2020

ASJC Scopus subject areas

  • Computer Science Applications
  • Physical and Theoretical Chemistry


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