Nuclear Quantum Effect and H/D Isotope Effect on Hydrogen-Bonded Systems with Path Integral Simulation

Abstract

In the past two decades, ab initio path integral (PI) simulation, in particular, ab initio path integral molecular dynamics simulation has reached its maturity and has been widely used to take account of nuclear quantum effects, such as zero-point vibrational energy and tunneling, in complex many-body systems. In particular, this method has significantly contributed to provide important insights into structures and fluctuation of the hydrogen-bonded systems as well as their isotopomers at finite temperature. In this chapter, we will review the recent advances in ab initio PI simulation. The development of an efficient algorithm for ab initio PI simulation and some applications will be featured. The efficient algorithm for path integral hybrid Monte Carlo method based on the second- and fourth-order Trotter expansion, which realizes large reduction of computational effort without loss of accuracy, will be described in detail. The applications focusing on the hydrogen-bonded systems, protonated and deprotonated water dimers (H5O2 + and H3O2 −), F−(H2O)n (n = 1–3) clusters, and hydrogen maleate anion demonstrate the ability and powerfulness of PI simulation.