晶体对称的不均衡分布及其原因探讨

An Approach to Unbalanced Distribution of Crystals in Symmetry and Its Cause

常见矿物晶体在各晶族、晶系、对称型、空间群中的分布,经统计是极不均衡的。在三大晶族中,以低级晶族矿物种数为最多(占1/2);七个晶系中,主要分布在单斜、斜方和等轴晶系中(占2/3以上);在23种对称型中,主要分布在2/m(L^2PC)、mmm(3L^23PC)和m3m(3L^4L^36L^29PC)三对称型中(占1/2以上);在230种空间群中,以P■、C2/m、P2_1/c、C2/cPbnm、Fm3m六空间群中分布矿物种数最多。造成这种极不均衡分布的原因主要由矿物的热力学特性和晶体内部质点的排布方式所决定。同时又受晶体的晶格类型、化学键的简繁程度,化学成份的特性及其复杂程度、离子半径等多种因素制约。

Statisties have confirmed that the distribution of common mineral crystals is unbalanced in the three crystal druses, the seven crystal systems, the thirty-two semmetry types as well as in the two-hundred-thirty space groups. They are distributed mainly in the lower druce(making up 1/2 of the total of common minerals), in the monoclinic, otherhombic and isometric systems(accounting for over 2/3 of the total), in the three symmetry types, 2/m(L^2PC), mmm(3L^23PC) and m3m(3L^4L^36L^2gPC) (amounting to more than 1/2 of the total), and in the following six space groups, P T C2/m, P2/c, C2/c, Pbnm and Fmam. The reasons for the notable unbalanced distribution chiefly lie in the thermodynamics Properties of mineral and the arrangement of crystal particles. It is also determined by such factors as the kind of crystal lattice, the characteristics of chemical bond, the features of chemical composition, ionic radius and the others.