Enabling Ab-Initio Molecular Dynamics under Bias: The CP2K+SMEAGOL Interface for Integrating Density Functional Theory and Non-Equilibrium Green Functions

TL;DR

This paper introduces a new interface between CP2K and SMEAGOL enabling ab-initio molecular dynamics simulations under bias by integrating DFT and NEGF methods, verified on various systems including large-scale condensed phases.

Contribution

The work presents the first implementation of a CP2K+SMEAGOL interface that allows DFT-NEGF calculations with current-induced forces for molecular dynamics under bias.

Findings

Good agreement with existing SMEAGOL calculations

Demonstrated molecular dynamics under bias for large condensed phase systems

First use of DFT-NEGF for molecular dynamics in realistic conditions

Abstract

Density functional theory (DFT) combined with non-equilibrium Greens functions (NEGF) is a powerful approach to model quantum transport under external bias potentials, at reasonable computational cost. In this work we present a new interface between the popular mixed Gaussian/plane wave electronic structure package CP2K and the NEGF code SMEAGOL, the most feature-rich implementation of DFT-NEGF available for CP2K to-date. The CP2K+SMEAGOL interface includes the implementation of current induced forces. We verify this implementation for a variety of systems: an infinite 1D Au wire, a parallel-plate capacitor and a Au-H2-Au junction. We find good agreement with SMEAGOL calculations performed with SIESTA for the same systems, and with the example of a solvated Au wire demonstrate for the first time that DFT-NEGF can be used to perform molecular dynamics simulations under bias of large-scale condensed phase systems under realistic operating conditions.