氟化鉀晶體屬立方晶系,用MoKα線(λ=70.8pm)拍攝衍射圖(相機半徑為57.4mm),各衍射線sin2θ值如下:0.0132,0.0256,0.0391,0.0514,0.0644,0.0769,0.102,0.115,0.127,0.139…… (1)先對各條衍射線指標化,然后推測KF的點陣形式,計算晶胞參數; (2)已知KF晶體中,負離子作立方最密堆砌,正離子填在八面體空隙,K+F-離子半徑分別為133和136pm,計算晶胞參數。
(1)立方體心點陣a=308pm (2)F-作堆積,K+填F-的立方體空隙,則a=310pm.
(1)ρ=0.917g×cm-3 (2)R(O-H…)=276.4pm