Regularized Perturbation Theory for Ab Initio Solids.

Area of Science:

• Computational physics
• Quantum chemistry
• Materials science

Background:

• Second-order Møller-Plesset perturbation theory (MP2) faces challenges in simulating solids, including divergence and overcorrelation issues.
• These limitations are particularly pronounced in metallic, narrow-gap, and dispersion-stabilized systems.

Purpose of the Study:

• To develop and evaluate novel regularized second-order perturbation theories for accurate *ab initio* simulations of solids.
• To assess the performance of these methods across diverse material classes, including metals, semiconductors, molecular crystals, and rare gas solids.

Main Methods:

• Development and application of three regularized second-order perturbation theories: κ-MP2, σ-MP2, and the size-consistent Brillouin-Wigner approach (BW-s2).
• Systematic assessment of these methods for calculating cohesive energies, lattice constants, and bulk moduli in various solid types.

Main Results:

• The Brillouin-Wigner approach (BW-s2) demonstrated high accuracy for cohesive energies, lattice constants, and bulk moduli in metals, semiconductors, and molecular crystals.
• BW-s2 performance rivaled or surpassed coupled-cluster with singles and doubles (CCSD) at a reduced computational cost.
• In rare gas solids, where standard MP2 underbinds, κ-MP2 showed minimal degradation, while BW-s2 encountered difficulties.

Conclusions:

• Regularized perturbation theories offer a promising avenue for efficient and accurate solid-state simulations, addressing limitations of standard MP2.
• BW-s2, particularly with specific parameterization (α = 2), emerges as a highly promising method, potentially outperforming contemporary random-phase approximations and coupled-cluster theories.
• Further validation across a broader range of systems is recommended to fully establish the capabilities of these advanced theoretical approaches.