Systematic Improvement of DMC Calculations in Transition Metal Oxides: sCI-Driven Wavefunction Optimization for Reliable Band Gaps predictions

• DOI: 10.48550/arxiv.2403.03466
• Publication Date: 2024-03-06
• Authors: Hyeondeok Shin; Kevin Gasperich; Tomás Rojas; Anh T. Ngo; Jaron T. Krogel; Anouar Benali
• Keywords: Chemical Physics (physics.chem-ph); Condensed Matter - Materials Science; Physics - Chemical Physics; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 01 natural sciences; 0104 chemical sciences

Accurate determination of electronic properties correlated oxides remains a significant challenge for computational theory. Traditional Hubbard-corrected density functional theory (DFT+U) frequently encounters limitations in precisely capturing electron correlation, particularly when predicting band gaps. We introduce systematic methodology to enhance the accuracy diffusion Monte Carlo (DMC) simulations both ground and excited states, focusing on LiCoO$_2$ as case study. By employing selected CI (sCI) approach, we demonstrate capability optimize wavefunctions beyond constraints single-reference DFT+U trial wavefunctions. show that sCI framework enables accurate prediction gaps LiCoO$_2$, closely aligning with experimental values substantially improving upon traditional methods. The study uncovers nuanced mixed state $t_{2g}$ $e_g$ orbitals at edges is not captured by conventional methods, further elucidating PBE+U describing $d$-$d$ excitations. Our findings advocate adoption beyond-DFT methodologies, such sCI, capture essential physics strongly materials. improved gap predictions ability generate more reliable DMC calculations underscore potential this approach broader applications oxides. This work only provides pathway structures complex materials but also suggests future investigations into states other challenging systems.