Abstract

The electronic energy-band structure of the PrBaCo₂O_5 + δ cobaltite at the oxygen content close to 5.5 are calculated by the first-principle PAW methods. The semiconductor–metal phase transition at 5 + δ = 5.5 is shown to be a result of the transition of cobalt atoms in the octahedral environment from the high-spin to low-spin state. The cause of the appearance of the metallic conduction is an increase in the energy of antibonding e_g states of pyramidal cobalt atoms, and, as a result, they are at the Fermi level, thereby determining the metallic character of the system. The effect of a deviation of the oxygen content from 5.5 on the energy-band structure and the conductivity is studied. The semiconductor–metal transition is shown can be observed only in a narrow range of the values of 5 + δ lower 5.5.

中文翻译：

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PrBaCo 2 O 5.5钴中的缺陷结构，电子能带结构和半导体-金属跃迁：从头算PAW方法

摘要

用第一性原理PAW法计算了氧含量接近5.5时的PrBaCo ₂ O _{5 +δ}钴的电子能带结构。半导体-金属在5 +δ= 5.5时的相变被证明是八面体环境中钴原子从高自旋态转变为低自旋态的结果。金属传导的外观的原因是在反键的能量的增加È_克锥体钴原子的原子态，因此它们处于费米能级，从而决定了系统的金属特性。研究了氧含量偏离5.5对能带结构和电导率的影响。所示的半导体-金属过渡仅在5 +δ的下限值5.5的狭窄范围内可以观察到。