Andrew J Medford | Searcharxiv

arXiv2026

Bulk Boundary Condition for Surface Calculations in Density Functional Theory

We present a bulk boundary condition formalism for surface calculations in Kohn--Sham density functional theory. The approach exploits the nearsightedness of electronic interactions in real space to restrict the calculation to a localized surface region. Within this region, the electron density is evaluated by leveraging the decay of the density matrix, with bulk values imposed on the density and electrostatic potential in the interior, and the electrostatic potential solved subject to bulk boundary conditions. The energy and atomic forces are computed using density-matrix-based expressions. Through representative calculations of surface and adsorption energies, we demonstrate the accuracy and efficiency of the proposed formalism.

cond-mat.mtrl-sci↗

arXiv2024

SPARC-X-API: Versatile Python Interface for Real-space Density Functional Theory Calculations

Density Functional Theory (DFT) is the de facto workhorse for large-scale electronic structure calculations in chemistry and materials science. While plane-wave DFT implementations remain the most widely used, real-space DFT provides advantages in handling complex boundary conditions and scaling to very large systems by allowing for the efficient use of large-scale supercomputers and linear-scaling methods that circumvent the cubic scaling bottleneck. The SPARC-X project (https://github.com/SPARC-X) provides highly efficient and portable real-space DFT codes for a wide range of first principle applications, available in both Matlab (M-SPARC) and C/C++ (SPARC). The rapid growth of SPARC's feature set has created the need for a fully functional interface to drive SPARC in high-throughput calculations. Here we introduce SPARC-X-API, a Python package designed to bridge the SPARC-X project with broader computational frameworks. Built on the atomic simulation environment (ASE) standard, the SPARC-X-API allows users to handle SPARC file formats and run SPARC calculations through the same interface as with other ASE-compatible DFT packages. Beyond standard ASE capabilities, SPARC-X-API provides additional features including 1) support of SPARC-specific setups, including complex boundary conditions and unit conversion, 2) a JSON schema parsed from SPARC's documentation for parameter validation and compatibility checks, and 3) a comprehensive socket communication layer derived from the i-PI protocol facilitating message passing between low-level C code and the Python interface. The goal of the SPARC-X-API is to provide an easy-to-use interface for users with diverse needs and levels of expertise, allowing for minimal effort in adapting SPARC to existing computational workflows, while also supporting developers of advanced real-space methods.

physics.chem-ph↗