The impact of transition metal (Ag) deficiencies on the structural and transport properties of ThCr₂Si₂-type arsenides are investigated. We experimentally confirm a partial occupancy of Ag in BaAg_2–xAs₂, which can be predictably controlled within 0.053(5) ≤ x ≤ 0.19(1) by varying the quenching temperature during the crystal growth. Density functional theory calculations reveal that substoichiometric concentrations of Ag lower the density of states at the Fermi level, providing an electronic cause for the tendency of Ag to form vacancies. This vacancy concentration is linked to a characteristic kink in electrical resistivity that can be substantially shifted from 22 to 125 K and is established as the metric of a low-temperature structural phase transition (SPT) in BaAg_2–xAs₂. Along with electrical resistivity, the Seebeck coefficient and heat capacity for selected BaAg_2–xAs₂ samples are presented, which also exhibit anomalies due to the SPT.

中文翻译：

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BaAg2–xAs2 中 Ag 空位的原因、后果和控制


研究了过渡金属 （Ag） 缺乏对 ThCr₂Si₂ 型砷化物结构和传输性能的影响。我们通过实验证实了 Ag 在 BaAg _2-xAs₂ 中的部分占据，这可以通过改变晶体生长过程中的淬火温度≤ 0.053（5） ≤ x 0.19（1） 范围内进行预测控制。密度泛函理论计算表明，Ag 的亚化学计量浓度降低了费米能级的态密度，为 Ag 形成空位的趋势提供了电子原因。这种空位浓度与电阻率的特征扭结有关，该扭结可以从 22 K 大幅转变为 125 K，并被确定为 BaAg _2-xAs₂ 中低温结构相变 （SPT） 的度量。除了电阻率外，还给出了选定的 BaAg _2-xAs₂ 样品的塞贝克系数和热容，这些样品也表现出由于 SPT 引起的异常。