AI and the World's Hard Problems · Chemistry & materials · arXiv · 2026-10-26
Low-variance force estimators for nuclear quantum mean forces
Quantum equilibrium structures can be sampled with classical molecular dynamics using a learned effective potential for a single path-integral replica, but mean-force estimates from fixed-replica path-integral molecular dynamics are noisy. The authors derive a scaled-gradient estimator with zero sampling variance for a one-dimensional harmonic oscillator and estimate a 4.7–57.5-fold reduction in constrained-sampling time for molecular tests. Potentials trained on these forces yield stable production simulations, from which quantum expectation values of position-dependent observables are obtained as classical ensemble averages.