Events

Past Event

Thesis Defense In Chemistry, Presented by Jack Weber

June 6, 2023
2:00 PM - 4:00 PM
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Pupin 329

Thesis Defense in Chemistry
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Developments in Auxiliary Field Quantum Monte Carlo for Molecules

Presented By Jack Weber

 

Abstract:
Phaseless Auxiliary Field Quantum Monte Carlo (ph-AFQMC) has in recent years emerged as a top contender for the reliable simulation of small molecules within chemical accuracy for a variety of applications, including multi-reference and transition metal containing compounds. In this talk I will present data benchmarking ph-AFQMC on transition metal compounds versus experiment, detailing the level of complexity (and thus cost) necessary in the trial wavefunction to remove the phaseless bias to within 1-2 kcal/mol. I then present data predicting the singlet triplet gaps of candidate annihilators for optical upconversion, highlighting the ability of ph-AFQMC and other methods to predict and rationalize activity. I will then briefly highlight two collaborations in which ph-AFQMC proved too expensive, but where alternate methods were adequate to make qualitative predictions. I present the development and effective implementation of an approach to reduce the scaling of the effective bottleneck for AFQMC calculations, the energy evaluation, based on the locality of electronic correlation. Finally, I outline the development and behavior of a new constraint to remove the sign problem in fermionic AFQMC, the linecut (lc-) constraint, which presents certain advantages over the commonly used phaseless constraint

 

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