Path Integral Techniques Make Precise Description of Quantum Nuclear Fluctuations Possible in Atomistic Modeling

High-order path integral factorizations promise faster convergence of quantum mechanical properties of nuclei in atomistic modelling. A method developed at the Laboratory of Computational Science and Modelling makes it easy to use them together with arbitrarily-complex descriptions of inter-atomic potentials.

The precise description of quantum nuclear fluctuations in atomistic modelling is possible by employ- ing path integral techniques, which involve a considerable computational overhead due to the need of simulating multiple replicas of the system. Many approaches have been suggested to reduce the required number of replicas. Among these, high-order factorizations of the Boltzmann opera- tor are particularly attractive for high-precision and low-temperature scenarios. Unfortunately, to date, several technical challenges have prevented a widespread use of these approaches to study the nuclear quantum effects in condensed-phase systems. An inexpensive molecular dynamics scheme has been devised that overcomes these limitations, thus making it possible to exploit the improved convergence of high-order path integrals without having to sacrifice the stability, convenience, and flexibility of conventional second-order techniques. The method has been implemented in the open-source code i-PI.