钙钛矿型结构亚硝酸盐和氰化物的分子体积

 绝大部分的亚硝酸盐和氰化物属于钙钛矿型结构,但有部分化合物为“反”钙钛矿型结构,充填空洞A位的阳离子的拓扑体积为0。阴离子团NO₂^-和CN^-的拓扑体积都近乎常数,分别为41.73ų和40.03ų,标准方差σ_n-1=1.516和σ_n-1=1.25。由此,进一步证明了原来的一套离子拓扑体积数值的普适性。“反”钙钛矿型结构中A位阳离子的平均半径r_A>1.00Å时,三价阳离子会产生扩容效应,其扩容系数大约是其本身拓扑体积的2倍;正钙钛矿型结构中,当A位是由半径较大的Cs⁺充填时,Cs⁺也会产生扩容效应,其扩容系数约为24ų。氰化物中结晶水分子的拓扑体积近乎常数,为24ų或0。

MOLECULAR VOLUME OF NITRITES AND CYANIDES WITH PEROVSKITE-STRUCTURE

Most of the nitrites and cyanides are of perovskite-structure,but a few of them have anti-perovskite-structure and their topological volume of the cation in the hole of A-position is zero. The topological volume of the anion radical NO₂^- and CN^- approximates to a constant, 41.73 ų and 40.03 ų, with σ_n-1= 1.51 and σ_n-1= 1.25, respectively, suggesting the validity of the values of the topological volume of cations and anions calculated in the authors’ previous studies. Nevertheless, for the nitrites and cyanides with anti-perovskite-structure, if the average radius of cations in the A-position is larger than 1.00 Å, the unitcell volume would expand by the three charged cations. The expanding coefficient of three charged cations is twice the topological volume of the cation itself. For the nitrites and cyanides with perovskite-structure, if the cation in the A-position is very large, such as the cation Cs⁺, it would also cause the expansion of unit-cell volume. The ex-pading coefficient of cation Cs⁺ is about 24 ų The crystal water in the cyanides approximates to a constant 24 ų or zero, depending on the distribution in the position A or B.