Quantum Monte Carlo Pair Orbital Wave Functions for Periodic Systems.

Area of Science:

• Condensed matter physics
• Quantum chemistry
• Computational materials science

Background:

• Accurate theoretical descriptions of electrons in periodic solids are crucial for understanding material properties.
• Existing methods often struggle with complex electronic correlations and large system sizes.
• Developing advanced quantum Monte Carlo techniques is essential for ab initio materials modeling.

Purpose of the Study:

• To derive novel many-body wave functions for quantum Monte Carlo simulations of periodic systems.
• To explicitly integrate over the Brillouin zone for improved accuracy in electronic structure calculations.
• To provide a versatile formalism applicable to diverse condensed matter phenomena.

Main Methods:

• Derivation of many-body single and multireference wave functions.
• Incorporation of an antisymmetric portion that integrates over the Brillouin zone.
• Construction of BCS-like determinants for singlets and Pfaffians for polarized states using pair orbitals.
• Generalization to spin-dependent interactions using two-component spinor pairs.

Main Results:

• Successfully derived ab initio wave functions for quantum Monte Carlo of periodic systems.
• The wave functions are based on BCS-like determinants and Pfaffians.
• The formalism explicitly integrates over the Brillouin zone, enhancing accuracy.
• Demonstrated broad applicability to quasiparticle band gaps, optical excitations, and complex Fermi surfaces.

Conclusions:

• The developed formalism offers a powerful new tool for ab initio electronic structure calculations in periodic systems.
• This approach enables accurate descriptions of electronic properties and excitations.
• The method's generalizability to spin-dependent interactions expands its utility to a wider range of materials and phenomena.