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arXiv · 2607.27679

Iterative minimization in reduced density matrix functional theory for periodic systems

Kai Luo·Jingang Han·Peize Lin·Daye Zheng·Mohan Chen·Xinguo Ren
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Abstract

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 \ce{H2}, 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 M\"uller functionals, SPG yields lower energies and more stable convergence than EBI. Applications to fractionally charged \ce{LiH}, dissociating \ce{H2} and \ce{N2} molecules, and equation of state of silicon show that the algorithm presented in this implementation is reliable and robust.

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Kai Luo, Jingang Han, Peize Lin, Daye Zheng, Mohan Chen, Xinguo Ren. 2026-07-30. Iterative minimization in reduced density matrix functional theory for periodic systems. https://arxiv.org/abs/2607.27679

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