Density functional-based molecular dynamics (DFMD) has emerged as the method of choice for realistic simulation of many complex physical processes and chemical reactions in the condensed phase. However, to obtain reasonably accurate or at least qualitatively correct results the use of hybrid or range-seperated exchange correlation functionals is often required. This can increase the computational effort by a factor of 10-100 or more compared to GGA functionals, frequently making DFMD simulations at the hybrid density functional level impractical. A number of schemes have been developed to reduce the computational cost including overlap-based screening of Hartree Fock exchange (HFX) integrals, and in particular the auxiliary density matrix method (ADMM). Nonetheless, the computational effort for realistic samples of materials (1000s of electrons) is still very large and the throughput is typically limited by the calculation of HFX forces. Here we present a simple method to further reduce the computational effort without significantly sacrificing accuracy. In our approach, the number of HFX integrals to compute is reduced by a statistical analysis of the resulting HFX force components. Those integrals that only have a nearly negligible contribution to the overall HFX force are excluded from the calculation for a certain number of molecular dynamics time steps. The resulting small error is subsequently corrected by means of a force error history. We have implemented this method in the CP2K simulation package and demonstrate the capabilities on sample systems of various types ranging from a simple water dimer, to the solvated hydroxyl radical and the interface between hematite and liquid water. For the latter system we obtain speed-ups of up to a factor of 3 at a negligible error in electronic and structural properties. In our contribution we will discuss ways to further improve the efficiency of our scheme.<br/>

Accelerating hybrid functional-based molecular dynamics simulation through screening of Hartree-Fock exchange forces

255th National Meeting (2018)

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