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arXiv 2403.03466cond-mat.mtrl-sciphysics.chem-ph
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过渡金属氧化物中量子蒙特卡洛计算的系统改进:sCI驱动的波函数优化实现可靠的带隙预测

Systematic Improvement of Quantum Monte Carlo Calculations in Transition Metal Oxides: sCI-Driven Wavefunction Optimization for Reliable Band Gap prediction

Hyeondeok Shin, Kevin Gasperich, Tomas Rojas, Anh T. Ngo, Jaron T. Krogel, Anouar Benali

AI总结:

本研究提出基于选态组态相互作用(sCI)优化波函数的方法,系统改进扩散蒙特卡洛(DMC)计算,以准确预测LiCoO₂的带隙,揭示传统DFT+U方法的局限,为强相关氧化物电子结构模拟提供更可靠途径。

摘要:

相关氧化物电子性质的准确确定仍然是计算理论面临的重大挑战。传统的Hubbard修正密度泛函理论(DFT+U)在精确捕捉电子关联方面经常遇到限制,特别是在预测带隙时。我们引入了一种系统方法,以提高扩散蒙特卡洛(DMC)模拟在基态和激发态下的准确性,并以LiCoO$_2$作为案例研究。通过采用选态组态相互作用(sCI)方法,我们展示了超越单参考DFT+U试探波函数限制来优化波函数的能力。我们表明,sCI框架能够准确预测LiCoO$_2$中的带隙,与实验值紧密对齐,并显著优于传统计算方法。该研究揭示了带边处$t_{2g}$和$e_g$轨道的一种微妙混合态,这种混合态是传统单参考方法无法捕捉的,进一步阐明了PBE+U在描述$d$-$d$激发方面的局限性。我们的发现主张采用超越DFT的方法(如sCI)来捕捉强相关材料中激发态波函数的基本物理特性。带隙预测准确性的提高以及为DMC计算生成更可靠试探波函数的能力,凸显了该方法在相关氧化物研究中更广泛应用的前景。这项工作不仅为复杂材料中电子结构的更准确模拟提供了途径,而且为未来研究其他具有挑战性系统的激发态提供了一个框架。

英文摘要:

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

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