离域电子
极化(电化学)
凝聚态物理
波函数
物理
几何相位
价(化学)
材料科学
可见的
电子
量子力学
化学
物理化学
出处
期刊:Ferroelectrics
[Informa]
日期:1994-01-01
卷期号:151 (1): 49-58
被引量:35
标识
DOI:10.1080/00150199408244722
摘要
Abstract Abstract A modern theory of the macroscopic electric polarization has been recently founded. Polarization itself is not an observable, while the polarization difference ΔP between any two crystal states can be measured, defined, and calculated as a bulk material property. An hysteresis cycle measures ΔP as the integrated current flowing through the sample: the present theory provides an expression for exactly this quantity. Being a current, ΔP is a property of the phases of the crystal wavefunctions, which can be cast as a Berry's phase, i.e. as a gauge-invariant phase feature of the valence Bloch orbitals. I stress that the periodic charge density of the polarized crystal-where any phase information is deleted-is irrelevant to macroscopic polarization. The present viewpoint elucidates the fundamental quantum nature of polarization: no Clausius-Mossotti-like model applies whenever the valence electrons are delocalized, as is the case in perovskites. Besides its conceptual importance, the Berry's phase approach provides a powerful algorithm, which has been implemented in the framework of the first-principles theory of materials.
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