85 / 2023-04-13 10:38:16

Implementation of plane-wave-based stochastic-deterministic density functional theory for extended systems in ABACUS

辐射和流体力学 > 高能量密度科学与温稠密物质-海报

Traditional Kohn-Sham density functional theory (KSDFT) is one of the most popular quantum-mechanics-based methods in modeling materials since it balances accuracy and efficiency well. However, traditional KSDFT based on the diagonalization method (DG) must solve all occupied bands. The number of bands rises with the increase of temperature and sizes, and the CPU time of KSDFT calculation scales as O(N³T³). Thus, it is inefficient to simulate large-size and high-temperature systems. The evaluation of the ground-state density in KSDFT can be replaced by the Chebyshev trace (CT) method. Recently, stochastic density functional theory^1,2 (SDFT) and its improved theory, mixed stochastic-deterministic density functional theory³ (MDFT) are developed based on the CT method and stochastic orbitals, which makes it possible to simulate large-size and high-temperature systems more efficiently. We have implemented the four methods based on the plane-wave basis set within the first-principles package ABACUS. In addition, all methods are adapted to the norm-conserving pseudopotentials and periodic boundary conditions using k-point sampling in the Brillouin zone. By testing the Si and C systems from the DG method as benchmarks, we systematically evaluate the accuracy and efficiency of the SDFT and MDFT methods by examining a series of physical properties, which include electron density, free energy, atomic forces, stress, and density of states. We conclude that they not only reproduce the DG results with sufficient accuracy but also exhibit several advantages over the DG method. We expect these methods can be of great help in studying both large-size systems and high-temperature systems.