Caravaca M A, Casali R A
Facultad de Ingenieria, Universidad Nacional del Nordeste, Avenida Las Heras 727, 3500-Resistencia, Argentina.
J Phys Condens Matter. 2005 Sep 21;17(37):5795-5811. doi: 10.1088/0953-8984/17/37/015.
The SIESTA approach based on pseudopotentials and a localized basis set is used to calculate the electronic, elastic and equilibrium properties of P 2/c, Pbca, Pnma, Fm3m, P4nmc and Pa3 phases of HfO. Using separable Troullier-Martins norm-conserving pseudopotentials which include partial core corrections for Hf, we tested important physical properties as a function of the basis set size, grid size and cut-off ratio of the pseudo-atomic orbitals (PAOs). We found that calculations in this oxide with the LDA approach and using a minimal basis set (simple zeta, SZ) improve calculated phase transition pressures with respect to the double-zeta basis set and LDA (DZ-LDA), and show similar accuracy to that determined with the PPPW and GGA approach. Still, the equilibrium volumes and structural properties calculated with SZ-LDA compare better with experiments than the GGA approach. The bandgaps and elastic and structural properties calculated with DZ-LDA are accurate in agreement with previous state of the art ab initio calculations and experimental evidence and cannot be improved with a polarized basis set. These calculated properties show low sensitivity to the PAO localization parameter range between 40 and 100 meV. However, this is not true for the relative energy, which improves upon decrease of the mentioned parameter. We found a non-linear behaviour in the lattice parameters with pressure in the P 2/c phase, showing a discontinuity of the derivative of the a lattice parameter with respect to external pressure, as found in experiments. The common enthalpy values calculated with the minimal basis set give pressure transitions of 3.3 and 10.8 GPa for [Formula: see text] and [Formula: see text], respectively, in accordance with different high pressure experimental values.
基于赝势和局域基组的SIESTA方法用于计算HfO的P 2/c、Pbca、Pnma、Fm3m、P4nmc和Pa3相的电子、弹性和平衡性质。使用包含Hf部分芯修正的可分离Troullier-Martins守恒规范赝势，我们测试了重要物理性质随基组大小、网格大小和赝原子轨道（PAO）截止比的变化。我们发现，采用LDA方法并使用最小基组（单ζ，SZ）对该氧化物进行计算，相对于双ζ基组和LDA（DZ-LDA），能改善计算得到的相变压力，并且与用PPPW和GGA方法确定的精度相似。尽管如此，用SZ-LDA计算得到的平衡体积和结构性质与实验结果的比较比GGA方法更好。用DZ-LDA计算得到的带隙、弹性和结构性质与先前的先进从头算计算和实验证据一致，并且不能通过极化基组得到改善。这些计算性质对PAO局域化参数在40到100 meV之间的范围显示出低敏感性。然而，相对能量并非如此，随着上述参数的减小，相对能量会得到改善。我们发现P 2/c相中晶格参数随压力呈现非线性行为，如实验中所发现的，a晶格参数相对于外部压力的导数存在不连续性。用最小基组计算得到的常见焓值给出[公式：见正文]和[公式：见正文]的压力转变分别为3.3 GPa和10.8 GPa，这与不同的高压实验值一致。
