Salles N, Martin-Samos L, de Gironcoli S, Giacomazzi L, Valant M, Hemeryck A, Blaise P, Sklenard B, Richard N
CNR-IOM/Democritos National Simulation Center, Istituto Officina dei Materiali, c/o SISSA, via Bonomea 265, Trieste, 34136, Italy.
Materials Research Laboratory, University of Nova Gorica, Vipavska 11c, 5270, Ajdovščina, Slovenia.
Nat Commun. 2020 Jul 3;11(1):3330. doi: 10.1038/s41467-020-17173-w.
In the context of ionic transport in solids, the variation of a migration barrier height under electric fields is traditionally assumed to be equal to the classical electric work of a point charge that carries the transport charge. However, how reliable is this phenomenological model and how does it fare with respect to Modern Theory of Polarization? In this work, we show that such a classical picture does not hold in general as collective dipole effects may be critical. Such effects are unraveled by an appropriate polarization decomposition and by an expression that we derive, which defines the equivalent polarization-work charge. The equivalent polarization-work charge is not equal neither to the transported charge, nor to the Born effective charge of the migrating atom alone, but it is defined by the total polarization change at the transition state. Our findings are illustrated by oxygen charged defects in MgO and in SiO.
在固体中的离子传输背景下，传统上认为电场下迁移势垒高度的变化等于携带传输电荷的点电荷的经典电功。然而，这个唯象模型有多可靠，它相对于现代极化理论的表现如何？在这项工作中，我们表明，由于集体偶极子效应可能很关键，这样的经典图像一般并不成立。通过适当的极化分解和我们推导的一个表达式可以揭示这些效应，该表达式定义了等效极化功电荷。等效极化功电荷既不等于传输电荷，也不等于单独迁移原子的玻恩有效电荷，而是由过渡态的总极化变化定义。我们的发现通过MgO和SiO中的氧带电缺陷来说明。
