Configuration path integral Monte Carlo with atomic orbitals.

Authors

Jingwei Xing, Jianmin Yuan

Published in

Physical review. E. Volume 114. Issue 3-2. Pages 035203.

Abstract

The configuration path integral Monte Carlo (CPIMC) method is employed to perform first-principles simulations of warm dense matter based on atomic orbitals. The system is modeled as an ion sphere with a pointlike nucleus at its center, and the electronic many-body problem is solved using CPIMC without approximations beyond the chosen Hamiltonian, basis truncation, and controllable statistical errors. Within this framework, estimators for the pressure and radial electron density are derived, and simulation schemes for the Gibbs and grand-canonical ensembles are formulated. Motivated by the η-ensemble concept in path integral Monte Carlo, a practical approach is developed to compute the partition function directly from an ideal grand-canonical reference system. To describe the dynamical coupling between electronic orbitals of the nearest-neighbor ion pairs, "substates" are introduced that combine bonding, antibonding, and continuum-like radial solutions, thereby providing a unified treatment of bound and continuum electrons and a flexible and model-controlled definition of ionization. The implementation is validated by comparing CPIMC simulations for neon using two distinct orbital basis sets, Hartree-Fock-Slater and hydrogen-like orbitals, yielding excellent agreement. The resulting equation of state is further compared with DFT-MD and RPIMC results for neon reported in the literature, showing good agreement in pressure and small deviations in internal energy. Finally, the substate extension is applied to beryllium in the canonical, grand-canonical, and Gibbs ensembles, and the results are compared with methods formulated in both the chemical and physical pictures. These results indicate that CPIMC with atomic orbitals is a promising route toward finite-temperature simulations of real materials in the warm dense regime, particularly for heavier elements.

PMID:
42888730
Bibliographic data and abstract were imported from PubMed on 17 Oct 2026.

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