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首页> 外文期刊>Acta Crystallographica, Section B. Structural science, crystal engineering and materials >Crystal structure, atomic net charges and electric moments in pyroelectric LiNaSO_4 at 296 K
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Crystal structure, atomic net charges and electric moments in pyroelectric LiNaSO_4 at 296 K

机译：热电LiNaSO_4在296 K时的晶体结构，原子净电荷和电矩

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摘要

The crystal structure and electric charge distribution in LiNaSO_4 have been studied at 296 K by X-ray diffraction using a spherical crystal. LiNaSO_4 is pyroelectric, nonferroelectric and an optically uniaxial insulator which crystallizes in the space group P31c. Least-squares refinement (MOLLY) was based on 13 026 reflections. The asymmetric unit contains Li~+, Na~+ and three SO_4~(2-) ions, where one O and S lie on a threefold axis about which three O atoms are related with a threefold symmetry in each sulfate ion. Two of the O-S-O groups suffer from disorder. The net charges of the atoms in three independent sulfate ions were determined under ionic charge constraints. The S atoms have positive net electric charges and O atoms are negative. The components of the significant electric multipole moments in the principal axis directions are determined from the distribution of net atomic charges in each sulfate ion. Electric moments in the unit cell generate macroscopic electric moments in the crystal which interact with light. This interaction results in two axial vectors of second rank associated with an optical indicatrix. The ratio of the calculated axial vector components in the principal axis directions originating from the asymmetric unit is 1.0061 (1), which compares well with the ratio of 1.006 for the corresponding optical refractive indices of LiNaSO_4 for λ_(Na) = 589.29 nm.
机译：通过使用球形晶体的X射线衍射研究了LiNaSO_4中的晶体结构和电荷分布，在296 K下。 LiNaSO 4是热电的，非铁电的并且是在空间群P31c中结晶的光学单轴绝缘体。最小二乘法（MOLLY）基于13 026个反射。不对称单元包含Li〜+，Na〜+和3个SO_4〜（2-）离子，其中一个O和S位于一个三重轴上，三个硫酸根原子在三个三轴上具有三个对称性。 O-S-O组中的两个患有疾病。在离子电荷约束下确定了三个独立的硫酸根离子中原子的净电荷。 S原子具有正净电荷，O原子为负。主轴方向的有效多极矩分量由每个硫酸根离子中的净原子电荷分布确定。晶胞中的电矩在晶体中产生与光相互作用的宏观电矩。这种相互作用导致与光学指示物相关联的第二等级的两个轴向向量。源自不对称单元的主轴方向上计算出的轴向矢量分量之比为1.0061（1），与λ_（Na）= 589.29 nm的LiNaSO_4的相应光学折射率的比率1.006很好。

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