Finite difference interpolation for accurate forces in real-space pseudopotential density functional theory

The high-order finite difference, real-space pseudopotential density functional theory (DFT) approach is a valuable method for large-scale, massively parallel DFT calculations. A significant challenge in the approach is the oscillating ``egg-box’’ error introduced by a coarse grid spacing. To address this issue while minimizing computational cost, we developed a finite difference interpolation scheme [1] of electron orbitals as a means of exploiting the high resolution of the pseudopotential to reduce egg-box effects systematically. We show an implementation of our method in PARSEC, a finite difference real-space pseudopotential DFT code [2] and demonstrate significant performance improvement in the computation of forces, leading to improved structural relaxations and molecular dynamics and achieving robust error mitigation at a fractional additional computational cost.





[1] Roller et al., J. Chem. Theory Comput. 19, 3889 (2023).

[2] Liou et al., J. Chem. Theory Comput. 17, 4039 (2021).