Institute of Theoretical Physics and Astronomy, Vilnius University, A. Goštauto Street 12, LT-01108 Vilnius, Lithuania.
J Chem Phys. 2013 Dec 14;139(22):224705. doi: 10.1063/1.4840435.
We present a first-principles investigation of structural and elastic properties of experimentally observed phases of bulk SrRuO3 - namely orthorhombic, tetragonal, and cubic - by applying density functional theory (DFT) approximations. First, we focus our attention on the accuracy of calculated lattice constants in order to find out DFT approaches that best represent the crystalline structure of SrRuO3, since many important physical quantities crucially depend on change in volume. Next, we evaluate single-crystal elastic constants, macroscopic elastic parameters, and mechanical stability trying to at least partially compensate for the existing lack of information about these fundamental features of SrRuO3. Finally, we analyze the anomalous behavior of low-temperature orthorhombic phase under C44 related shear deformation. It turns out that at critical strain values the system exhibits a distinct deviation from the initial behavior which results in an isosymmetric phase transition. Moreover, under C44 related shear deformation tetragonal SrRuO3 becomes mechanically unstable raising an open question of what makes it experimentally observable at high temperatures.
我们通过应用密度泛函理论（DFT）近似，对实验观察到的块状 SrRuO3 的相，即正交相、四方相和立方相的结构和弹性性质进行了第一性原理研究。首先，我们关注计算晶格常数的准确性，以找到最能代表 SrRuO3 晶体结构的 DFT 方法，因为许多重要的物理量都取决于体积的变化。接下来，我们评估单晶弹性常数、宏观弹性参数和力学稳定性，试图至少部分弥补关于 SrRuO3 这些基本特征的现有信息不足。最后，我们分析了低温正交相在 C44 相关剪切变形下的异常行为。结果表明，在临界应变值下，系统表现出与初始行为明显的偏离，导致等对称相变。此外，在 C44 相关剪切变形下，四方相 SrRuO3 变得不稳定，这引发了一个悬而未决的问题，即是什么使得它在高温下具有实验可观测性。
