The hybrid Quantum Trajectory/Electronic Structure DFTB-based approach to Molecular Dynamics

Abstract

This paper describes a quantum trajectory (QT) approach to molecular dynamics with quantum corrections on behavior of the nuclei interfaced with the on-the-fly evaluation of electronic structure (ES). Nuclear wavefunction is represented by an ensemble of trajectories, concurrently propagated in time under the influence of the quantum and classical forces. For scalability to high-dimensional systems (hundreds of degrees of freedom), the quantum force is computed within the Linearized Quantum Force (LQF) approximation. The classical force is determined from the ES calculations, performed at the Density Functional Tight Binding (DFTB) level. High throughput DFTB version is implemented in a massively parallel environment using Open MP/MPI. The dynamics has also been extended to describe the Boltzmann (imaginary-time) evolution defining temperature of a molecular system. The combined QTES-DFTB code has been used to study reaction dynamics of systems consisting of up to 111 atoms.