Santana Juan A, Krogel Jaron T, Kim Jeongnim, Kent Paul R C, Reboredo Fernando A
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
J Chem Phys. 2015 Apr 28;142(16):164705. doi: 10.1063/1.4919242.
We have applied the many-body ab initio diffusion quantum Monte Carlo (DMC) method to study Zn and ZnO crystals under pressure and the energetics of the oxygen vacancy, zinc interstitial, and hydrogen impurities in ZnO. We show that DMC is an accurate and practical method that can be used to characterize multiple properties of materials that are challenging for density functional theory (DFT) approximations. DMC agrees with experimental measurements to within 0.3 eV, including the band-gap of ZnO, the ionization potential of O and Zn, and the atomization energy of O2, ZnO dimer, and wurtzite ZnO. DMC predicts the oxygen vacancy as a deep donor with a formation energy of 5.0(2) eV under O-rich conditions and thermodynamic transition levels located between 1.8 and 2.5 eV from the valence band maximum. Our DMC results indicate that the concentration of zinc interstitial and hydrogen impurities in ZnO should be low under n-type and Zn- and H-rich conditions because these defects have formation energies above 1.4 eV under these conditions. Comparison of DMC and hybrid functionals shows that these DFT approximations can be parameterized to yield a general correct qualitative description of ZnO. However, the formation energy of defects in ZnO evaluated with DMC and hybrid functionals can differ by more than 0.5 eV.
我们应用多体从头算扩散量子蒙特卡罗（DMC）方法来研究压力下的锌（Zn）和氧化锌（ZnO）晶体，以及氧化锌中氧空位、锌间隙原子和氢杂质的能量学。我们表明，DMC是一种准确且实用的方法，可用于表征对密度泛函理论（DFT）近似具有挑战性的材料的多种性质。DMC与实验测量值的误差在0.3电子伏特以内，包括氧化锌的带隙、氧和锌的电离势，以及氧气、氧化锌二聚体和纤锌矿型氧化锌的原子化能。DMC预测，在富氧条件下，氧空位是一个深施主，形成能为5.0(2)电子伏特，其热力学跃迁能级位于距价带顶1.8至2.5电子伏特之间。我们的DMC结果表明，在n型以及富锌和富氢条件下，氧化锌中锌间隙原子和氢杂质的浓度应该较低，因为在这些条件下，这些缺陷的形成能高于1.4电子伏特。DMC与杂化泛函的比较表明，这些DFT近似可以进行参数化，以对氧化锌给出大致正确的定性描述。然而，用DMC和杂化泛函评估的氧化锌中缺陷的形成能可能相差超过0.5电子伏特。
