Overcoming finite-size effects in electronic structure simulations at extreme conditions

Area of Science:

• Computational Physics
• Quantum Many-Body Systems

Background:

• Ab initio quantum Monte Carlo (QMC) methods are powerful for simulating electron systems.
• Simulations are typically limited by finite system sizes (N electrons) and periodic boundary conditions.
• Accurate theories for finite-size effects are needed to reach the thermodynamic limit.

Purpose of the Study:

• To develop a novel scheme for eliminating finite-size effects in QMC simulations.
• To accurately determine properties of the uniform electron gas at finite temperatures.
• To enable reliable calculations relevant to warm dense matter.

Main Methods:

• Utilized the density response formalism.
• Developed a new scheme to correct for finite-size effects in the static structure factor S(q) and interaction energy v.
• Applied methods to the uniform electron gas at finite temperatures.

Main Results:

• The new scheme effectively removes finite-size effects.
• Obtained the interaction energy v in the thermodynamic limit with high accuracy (∼0.2%).
• Achieved accurate results using a small number of electrons (N=4) without empirical parameters.

Conclusions:

• The developed method provides a robust way to eliminate finite-size effects in QMC.
• Enables accurate calculations for the thermodynamic limit relevant to warm dense matter.
• Demonstrated applicability across a range of densities (r_s) and temperatures (T).