Abstract The substitutional solute atom induced local lattice distortion (LLD) in dilute metal solid solution was believed to be uniform because the solute atom was supposed to occupy the high symmetry lattice site without breaking the point group symmetry of the crystal lattice. Contrary to this conventional picture, we report in this paper that substitutional Mo atom in Ti-Mo solid solution occupies an off-center position instead of the high symmetry lattice site and leads to highly non-uniform LLD, as evidenced by our first principles calculations. The physics underlying the off-center occupation and non-uniform LLD are shown to be the Jahn-Teller splitting of the degenerated d states of Mo atom. With which, the solid-solutions suffering from non-uniform LLD are predicted. The non-uniform LLD challenges the application of classical solid solution hardening model based on uniform LLD and spherical stress tensor assumption to this kind of solid solutions. This work also questions the traditional view that elementary substitutional solute atoms in metal solid solutions should not induce anelastic relaxation and internal friction.

中文翻译：

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稀Ti-Mo固溶体中非常规非均匀局部晶格畸变

摘要 置换溶质原子在稀金属固溶体中引起的局部晶格畸变（LLD）被认为是均匀的，因为溶质原子应该占据高对称晶格位而不破坏晶格的点群对称性。与此传统图片相反，我们在本文中报告说，Ti-Mo 固溶体中的替代 Mo 原子占据偏心位置而不是高对称晶格位点，并导致高度不均匀的 LLD，如我们的第一性原理计算所证明的. 偏心占据和非均匀 LLD 的基础物理被证明是 Mo 原子的简并 d 态的 Jahn-Teller 分裂。用它来预测具有非均匀 LLD 的固溶体。非均匀 LLD 挑战了基于均匀 LLD 和球面应力张量假设的经典固溶强化模型在此类固溶体中的应用。这项工作还质疑传统观点，即金属固溶体中的基本置换溶质原子不应引起弹性松弛和内摩擦。