Improved Fast Randomized Iteration Approach to Full Configuration Interaction
Abstract
We present three modifications to our recently introduced fast randomized iteration method for full configuration interaction (FCIFRI) and investigate their effects on the method's performance for Ne, H$_2$O, and N$_2$. The initiator approximation, originally developed for full configuration interaction quantum Monte Carlo, significantly reduces statistical error in FCIFRI 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.
 Publication:

arXiv eprints
 Pub Date:
 May 2020
 arXiv:
 arXiv:2005.00654
 Bibcode:
 2020arXiv200500654G
 Keywords:

 Physics  Computational Physics;
 Condensed Matter  Strongly Correlated Electrons;
 Physics  Chemical Physics
 EPrint:
 13 pages, 5 figures