Periodic Local Coupled-Cluster Theory for Insulators and Metals

Area of Science:

• Computational Chemistry
• Condensed Matter Physics
• Materials Science

Background:

• Coupled-cluster theory is a high-accuracy quantum chemistry method.
• Periodic boundary conditions are essential for solid-state materials.
• Local approximations and natural orbitals can reduce computational cost.

Purpose of the Study:

• To detail the implementation of periodic local coupled-cluster theory.
• To explore choices for orbital localization, fragmentation, and local natural orbital construction.
• To assess the efficiency and accuracy for crystalline solids.

Main Methods:

• Periodic local coupled-cluster theory with single and double excitations (CCSD) and perturbative triple excitations [CCSD(T)].
• Utilization of local natural orbitals (LNOs) and k-point symmetry.
• Comparison of different orbital localization and fragmentation strategies.

Main Results:

• Demonstrated applicability to both insulators (diamond) and metals (lithium).
• Achieved computational speedups of 2-3 orders of magnitude.
• Obtained accurate predictions for cohesive energy, lattice constant, and bulk modulus.

Conclusions:

• Periodic LNO-CC theory is a robust and efficient method for solid-state calculations.
• The approach shows excellent agreement with experimental and previous theoretical data.
• Significant computational gains are realized even for moderate k-point meshes.