用Cu-Kα射線(λ=0.154nm)作金屬鉬(立方晶系)晶體粉末衍射圖,在θ=20.250,27.300,36.820,43.810,50.690,58.000,66.300等有衍射峰,求: ①鉬的晶體結(jié)構(gòu)屬于哪一種點(diǎn)陣形式? ②鉬的晶胞參數(shù)?