Quantum Chemistry for Molecules at Extreme Pressure on Graphical Processing Units: Implementation of Extreme Pressure Polarizable Continuum Model

Pressure plays essential roles in chemistry by altering structures and controlling chemical reactions. The extreme-pressure polarizable continuum model (XP-PCM) is an emerging method with an efficient quantum mechanical description of molecules at high pressure (on the order of GPa), but its application to large molecular systems was previously hampered by CPU computation bottleneck. Here, we exploit advances in Graphical Processing Units (GPUs) to accelerate XP-PCM calculations and enable quantum chemistry simulation of large molecular and biomolecular systems under high pressure. We benchmarked the performance using 18 small proteins in aqueous solutions. Using a single GPU, our method evaluates the density functional theory (DFT) single point energy of a protein with over 500 atoms and 4000 basis functions under extreme pressure within half an hour. The time taken by the XP-PCM-integral evaluation is typically 1% of the time taken for a gas phase DFT calculation on the same system. The overall XP-PCM calculations require less computational effort than that for their gas-phase counterpart due to the improved convergence of self-consistent field iterations. Therefore, the description of the high-pressure effects with our GPU accelerated XP-PCM is feasible for any molecule tractable for gas-phase DFT calculation. To validate the accuracy of our method, we evaluated the free energy of argon, whose properties under high pressure are known from experiments. The pressure-volume relationship predicted by our method matches previous theoretical and experimental results.