Communication: Compact orbitals enable low-cost linear-scaling ab initio molecular dynamics for weakly-interacting systems

Abstract

Today, ab initio molecular dynamics (AIMD) relies on the locality of one-electron density matrices to achieve linear growth of computation time with the system size, crucial in large-scale simulations. While Kohn-Sham orbitals strictly localized within predefined radii can offer substantial computational advantages over density matrices, such compact orbitals are not used in AIMD because a compact representation of the electronic ground state is difficult to find. Here, a robust method for maintaining compact orbitals close to the ground state is coupled with a modified Langevin integrator to produce stable nuclear dynamics for molecular and ionic systems. This eliminates a density matrix optimization and enables first orbital-only linear-scaling AIMD. An application to liquid water demonstrates that low computational overhead of the new method makes it ideal for routine medium-scale simulations, while its linear-scaling complexity allows us to extend first-principle studies of molecular systems to completely new physical phenomena on previously inaccessible length scales.

Reconciling the Experimental and Computational Hydrogen Evolution Activities of Pt(111) through DFT-Based Constrained MD Simulations

“…A variation of this magnitude is easily sufficient to result in immense margins of errors for macroscopic current densities. Although the spatial (cell size) and temporal (simulation length) requirements for obtaining tightly converged electrode potentials present a major obstacle together with the lack of a "perfect" functional, workarounds such as charge constrained DFT (cDFT) 99 and linear-scaling DFT-MD algorithms 100 extending the accessible length scale of routine simulations to more than 10 4 atoms are expected to pave the way for more accurate electrochemical modeling. Until then, the present work represents nevertheless one of the most extensive and realistic simulations of HER on Pt(111) based on an explicit, fully dynamic first-principles approach.…”

CP2K: An Electronic Structure and Molecular Dynamics Software Package -- Quickstep: Efficient and Accurate Electronic Structure Calculations

“…Here, they are referred to as compact localized molecular orbitals (CLMOs) to emphasize that their expansion coefficients are set to zero for all basis functions centered outside orbitals' localization subsets. Unlike previous works [208][209][210], the ALMO acronym is avoided [203], since it commonly refers to a special case of compact orbitals with R c = 0 [211][212][213][214][215][216].…”

“…An application of CLMO AIMD to liquid water demon- strates that the compensating terms in the modified Langevin equation can be tuned to maintain a stable dynamics and reproduce accurately multiple structural and dynamical properties of water with tight orbital localization (R c = 1.6 vdWR) and SCF as high as 10 −2 a.u. [210].…”

“…Extension of ALMO EDA to AIMD simulations have shown that the insignificant covalent component of HB determines many unique properties of liquid water including its structure (Fig. 8), dielectric constant, hydrogen bond lifetime, rate of self-diffusion and viscosity [210,289].…”

Accurate Sampling with Noisy Forces from Approximate Computing

“…8 is satisfied [Berendsen et al 1984;Khaliullin and Kühne 2013;Kühne et al 2009]. Alternatively, γ N can be computed by integrating the autocorrelation function of the additive white noise [Scheiber et al 2018]. In Table 2 Fig.…”