Auxiliary-field quantum Monte Carlo study of first- and second-row post-d elements.

Area of Science:

• Computational Chemistry
• Quantum Many-Body Physics

Background:

• Accurate electronic structure calculations are crucial for understanding chemical properties.
• Post-d elements present significant computational challenges due to electron correlation effects.

Purpose of the Study:

• To apply the phaseless auxiliary-field quantum Monte Carlo (AF QMC) method to first- and second-row post-d elements.
• To assess the accuracy of AF QMC by comparing results with experimental data and other high-level computational methods.

Main Methods:

• Utilized the phaseless auxiliary-field quantum Monte Carlo (AF QMC) method.
• Employed a Hartree-Fock trial wave function and consistent correlated basis sets with small-core relativistic pseudopotentials.
• Performed calculations for Ga-Br and In-I elements.

Main Results:

• AF QMC total energies closely matched coupled-cluster singles, doubles, and triples (CCSD(T)) results across various basis sets.
• Calculated atomic electron affinities, ionization energies, and dimer spectroscopic properties demonstrated excellent agreement with experimental values.
• The phaseless approximation effectively addressed the phase/sign problem in the quantum Monte Carlo calculations.

Conclusions:

• The phaseless AF QMC method provides a reliable and accurate approach for electronic structure calculations of post-d elements.
• AF QMC offers a viable alternative to traditional methods like CCSD(T) for studying these challenging systems.
• The study validates the efficacy of AF QMC in predicting fundamental chemical properties.