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Starting-point-independent quantum Monte Carlo calculations of iron oxide

机译：起始点无关量子蒙特卡罗氧化铁计算

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摘要

Quantum Monte Carlo (QMC) methods are useful for studies of strongly correlated materials because they are many body in nature and use the physical Hamiltonian. Typical calculations assume as a starting point a wave function constructed from single-particle orbitals obtained from one-body methods, e.g., density functional theory. However, mean-field-derived wave functions can sometimes lead to systematic QMC biases if the mean-field result poorly describes the true ground state. Here, we study the accuracy and flexibility of QMC trial wave functions using variational and fixed-node diffusion QMC estimates of the total spin density and lattice distortion of antiferromagnetic iron oxide (FeO) in the ground state B1 crystal structure. We found that for relatively simple wave functions the predicted lattice distortion was controlled by the choice of single-particle orbitals used to construct the wave function, rather than by subsequent wave function optimization techniques within QMC. By optimizing the orbitals with QMC, we then demonstrate starting-point independence of the trial wave function with respect to the method by which the orbitals were constructed by demonstrating convergence of the energy, spin density, and predicted lattice distortion for two qualitatively different sets of orbitals. The results suggest that orbital optimization is a promising method for accurate many-body calculations of strongly correlated condensed phases.
机译：Quantum Monte Carlo（QMC）方法对于研究强烈相关的材料是有用的，因为它们是自然界的许多身体并使用物理汉密尔顿人。典型的计算假设作为从一体方法获得的单粒子轨道构成的波函数，例如密度泛函理论。然而，如果平均场结果描述真正的地位，则平均场导出的波函数有时会导致系统QMC偏置。在这里，我们使用变分和固定节点扩散QMC估计在地态B1晶体结构中使用变分和固定节点扩散QMC估计来研究QMC试验波函数的精度和灵活性，并在地态B1晶体结构中的反铁磁氧化铁（FEO）的晶格变形。我们发现，对于相对简单的波函数，通过选择用于构造波函数的单粒子轨道来控制预测的晶格失真，而不是通过QMC内的后续波函数优化技术来控制。通过用QMC进行轨道来优化轨道，我们通过展示能量，自旋密度和预测的两个定性不同组的晶格变形来构建轨道构成的方法的试验波功能的起点独立性轨道。结果表明，轨道优化是准确多体计算强相关的凝聚阶段的有希望的方法。

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  • 来源
    《Physical review》 |2020年第15期|155151.1-155151.7|共7页
  • 作者

    Joshua P. Townsend; Sergio D. Pineda Flores; Raymond C. Clay Ⅲ; Thomas R. Mattsson; Eric Neuscamman; Luning Zhao; R. E. Cohen; Luke Shulenburger;

  • 作者单位

    High Energy Density Physics Theory Sandia National Laboratories Albuquerque New Mexico 87185 USA;

    Department of Chemistry University of California Berkeley California 94720 USA;

    High Energy Density Physics Theory Sandia National Laboratories Albuquerque New Mexico 87185 USA;

    High Energy Density Physics Theory Sandia National Laboratories Albuquerque New Mexico 87185 USA;

    Department of Chemistry University of California Berkeley California 94720 USA;

    Department of Chemistry University of Washington Seattle Washington 98195 USA;

    Extreme Materials Initiative Earth and Planets Laboratory Carnegie Institution for Science Washington DC 20015-1305 USA;

    High Energy Density Physics Theory Sandia National Laboratories Albuquerque New Mexico 87185 USA;

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