Relativistic diffusion Monte Carlo method: zeroth-order regular approximation-diffusion Monte Carlo method in a...

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Relativistic Quantum Chemistry

Background:

• Accurately describing relativistic effects is crucial for heavy elements.
• Electron correlation significantly impacts molecular properties.
• Combining these effects computationally remains a challenge.

Purpose of the Study:

• To develop a novel diffusion Monte Carlo (DMC) method incorporating the relativistic zeroth-order regular approximation (ZORA).
• To enable simultaneous treatment of relativistic and electron-correlation effects in quantum chemical calculations.

Main Methods:

• Derivation of a new approximate Green's function for the spin-free ZORA Hamiltonian.
• Implementation of a relativistic cusp-correction scheme.
• Application of the combined ZORA-DMC method to atoms and small molecules.

Main Results:

• The ZORA-DMC method successfully incorporates both relativistic and electron-correlation effects.
• Recovered correlation energies are comparable to nonrelativistic DMC.
• Results show superiority over coupled cluster methods for certain basis sets.
• Accurate estimation of the dissociation energy for the CuH molecule.

Conclusions:

• The proposed ZORA-DMC method provides a robust framework for relativistic quantum chemistry.
• It offers a reliable way to compute accurate molecular properties for systems with heavy elements.
• The method demonstrates good agreement with experimental data.