Powered by Indico
v3.2.8
Speaker: Siyuan Chen (College of William and Mary)
Title: Interatomic forces and geometry optimization in solids with plane-wave auxiliary-field quantum Monte Carlo
Abstract: In this talk, I will discuss the computations of accurate interatomic forces in plane-wave AFQMC, and apply those to a geometry optimization procedure in solids. AFQMC is known as an excellent many-body total energy method. Recent implementation of the back-propagation technique in plane-wave AFQMC has paved the way to computations of non-energy observables like charge density and correlation functions. Using the Hellmann-Feynman Theorem, computations of interatomic forces in the plane-wave scheme are also straightforward, without the need for Pulay corrections. We benchmarked the calculated forces with the derivatives of AFQMC total energy in a simple system. Despite the accurate force results, high-dimensional and statistically noisy energy landscapes from many-body solid calculations can bring up various computational difficulties in geometry optimization. To address the problem, we developed a semi-automatic geometry optimization procedure, based on our improvement of the classical steepest descent method. This relatively inexpensive and stable procedure can be potentially extended to solids with geometry optimization challenges.