晶体结构 14 Bravais lattices 32 point groups Crystal system Table 2.7 Symbols of crystallographic point groups. Crystal First position Second position Third position Point group system Triclinic Element Direction Element Direction Element Direction Triclinic 1orI N/A None None 1,i Monoclinic Monoclinic 2,m or 2/m Y None None 2,m,2/m Orthorhombic 2 or m 2orm 上 2orm Z 222,mm2,mmm 4.4or Z None or X 4,4.4/m,422, Orthorhombic Tetragonal None or Base 4/m 2orm 2orm diagonal 4mm,42m, 4/mmm Tetragonal Trigonal 3 or 3 Z None or X None 3,3,32,3m,3m 2orm Hexagonal 6,6 or 6/m Z None orX None or Base 6,6.6/m,622, Hexagonal,Trigonal 2 or m 2orm diagonal 6mm,62m, 6/mmm Cubic 2,m.4 3 or3 Body None or Face 23,m3,432,43m, Cubie or4 diagonal 2 or m diagonal m3m 2晶体结构 14 Bravais lattices 32 point groups 2 Z