2026/07/30 by Kai Luo, Jingang Han, Peize Lin +3
Physics and Astronomy · #cond-mat.str-el
17 pages, 6 figures
arxiv created 2026/07/30 · arxiv updated 2026/07/31
Reduced density matrix functional theory (RDMFT) offers a route beyond Kohn-Sham density functional theory for strongly correlated systems, yet practical calculations for periodic solids are still out of reach. We formulate RDMFT for extended systems in a basis-independent way and present a planewave implementation using iterative minimization for periodic solids, evaluating nonlocal exchange-correlation functionals through the existing adaptive compressed exchange machinery. Natural occupations are optimized under N-representability constraints with a spectral projected gradient (SPG) method or an first-order explicit-by-implicit (EBI) map, while natural orbitals are updated by Riemannian optimization on the complex Stiefel manifolds. Benchmarks on typical systems of \ceH2, silicon, and sodium with the Hartree-Fock functional show that SPG reproduces converged hybrid references, whereas EBI can stall when occupations approach 0 or 1. With the power and Müller functionals, SPG yields lower energies and more stable convergence than EBI. Applications to fractionally charged \ceLiH, dissociating \ceH2 and \ceN2 molecules, and equation of state of silicon show that the algorithm presented in this implementation is reliable and robust.