Structural Considerations and Polarization Energy of Some PbFCl-Type Compounds
Structural Considerations and Polarization Energy of Some PbFCl-Type Compounds
复制标题
一些 PbFCl 类化合物的结构考虑和极化能
DOI：
--
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
J. Morel
中科院分区：
文献类型：
--
作者：
M. Sieskind;J. Morel
摘要：matlocite族的离子化合物MXY （pbcl）具有阴离子X和Y周围对称的特征。如果围绕离子X和Y的笼是规则的，那么晶体就被称为“规则的”，这些对称条件给出了四个足以计算晶格参数的方程。此外，对称性在某些物理性质上起着决定性的作用，因为它们是产生偶极矩的电子扭曲的起源。更准确地说，应该提到的是，X没有偶极矩，因为作用在X上的场是零，只有阳离子M和阴离子Y可能有偶极矩。诱导矩和极化能的相互作用都有助于稳定晶格。局部对称性与极化能之间的关系及其随压力的变化将被研究。在PbFI的情况下，随着压力的增加，离子I在细胞内的运动变得更加有规律。同时，离子I和Pb上的电场和诱导矩发生相反的变化，使极化能减小。这种效应只对高极化离子I可见，对Cl可以忽略不计。
Abstract Some ionic compounds MXY of the matlockite family (PbFCl) are characterized by the symmetry of the anions X and Y surroundings. If the cage around the ions X and Y are regular, the crystal is said to be “regular” and these conditions of symmetry give four equations adequate to compute the lattice parameters. Moreover, the symmetries play a decisive part on some physical properties because they are at the origin of electronic distorsions that produce dipolar moments. More precisely, it should be mentioned that X has no dipolar moment because the field acting on X is zero and that only the cation M and the anion Y may have dipolar moments. Both the interactions of the induced moments as well as the polarization energy contribute to stabilize the lattice. Relations between local symmetries and polarization energy and its variation with pressure will be investigated. In the case of PbFI, with an increase in pressure the ion I moves in the cell which becomes more regular. At the same time, opposite variations of the fields and of the induced moments on the ions I and Pb occur so that the polarization energy decreases. This effect is only observable with the highly polarizable ion I and is negligible for Cl.