2013晶体学第七章.ppt

_symmetry_cell_settingMonoclinic_symmetry_space_group_name_H-MPn_symmetry_equiv_pos_as_xyzx,y,zx+1/2,-y,z+1/2_cell_length_a3.9630(3)_cell_length_b11.0210(9)_cell_length_c8.7098(7)_cell_angle_alpha90.00_cell_angle_beta101.456(5)_cell_angle_gamma90.00_cell_volume372.83(5)_cell_formula_units_Z2S1S0.4980(5)0.13296(18)0.7880(2)S2S0.6837(3)0.08389(15)0.48270(17)S3S0.8720(4)0.17942(15)0.1787(2)S4S0.6976(3)0.33170(13)0.60625(16)S5S0.8828(4)0.43139(16)0.3049(2)O1O1.0496(11)0.3738(3)0.0207(5)C1C0.6216(13)0.1800(5)0.6355(8)C2C0.7833(17)0.1996(6)0.3650(8)C3C0.9477(17)0.3377(7)0.1491(8)C4C0.7882(18)0.3143(6)0.4211(8)r(O1,S1)=7.893Cm={?(ua+vb+wc)∪(ua+vb+wc+a/2+b/2)}∧{1;m{x,0,z}}Ca={?(ua+vb+wc)∪(ua+vb+wc+a/2+b/2)}∧{1;(m{x,0,z},a/2)}两式等价,(m{x,0,z},a/2+b/2)=(m{x,1/4,z},a/2)=a{x,1/4,z}与(m{x,0,z},a/2)=a{x,0,z}为同类型的滑移。Cc={?(ua+vb+wc)∪(ua+vb+wc+a/2+b/2)}∧{1;(m{x,0,z},c/2)}为新的空间群。Cn={?(ua+vb+wc)∪(ua+vb+wc+a/2+b/2)}∧{1;(m{x,0,z},(a+c)/2)}令c=a+c,即c=c-a,则上式为Cn={?(ua+vb+wc)∪(ua+vb+wc+a/2+b/2)}∧{1;(m{x,0,z},c/2)}可见,Cn群与Cc群等价。晶系点阵点群P空间群单斜mP(2/m)mC(2/m)2,m,2/mP2,Pm,P2/m,C2,Cm,C2/mP21,Pc,P21/m,P2/c,P21/cCc,C2/cCcP21/c定理7-3:空间群的中心对称与否取决于其点群的中心对称与否。ByheartSomeplaysaresosuccessfulthattheyrunforyearsonend,Inmanyways,thisisunfortunateforthepooractorswhoarerequiredtogoonrepeatingthesamelinesnightafternight.Onewouldexpectthemtoknowtheirpartsbyheartandneverhavecausetofalter.Yetthisisnotalwaysthecase.AfamousactorinahighlysuccessfulplaywasoncecastintheroleofanaristocratwhohadbeenimprisonedintheBastillefortwentyyears.Inthelastact,agao