氧离子的最紧密堆积构造与矿物的平均折光率之关系

本文论述了37个氧离子作最紧密堆积的矿物,指出其平均折光率与结晶构造的定量关系。推导出“法扬斯常数”。阐明轻元素Li,Be,Na,Mg,Al对折光率的影响无显著差別;而第四周期的“重”元素如Ca,Sc,Ti,Cr,Mn,Fe都使折光率增高,这是与这些离子失去4s和3d电子有关,尤以失去3d电子对折光率增高影响最大。

ON THE RELATION BETWEEN THE STRUCTURES OF CLOSEST PACKING OF OXYGEN ANIONS AND THE MEAN REFRACTIVE INDICES OF MINERALS

Thirty-seven minerals with the structures of closest packing of oxygen anions are discussed in this paper. The quantitative relation between the mean refractive indices （m.r.i.） and the structures of these minerals is pointed out. The constant, called as "Fajans’ constant" by the author, is derived. The essentially similar effect of light elements such as Li, Be, Na, Mg, Al on the m.r.i, of minerals is pointed out. On the other hand, the "heavy elements" of the fourth period such as Ca, Sc, Ti, Cr, Mn, Fe, show noticeable effects on the increase in the index of refraction, which is probably caused by the removal of 4s or 4s3d electrons, particularly the more important removal of 3d electrons in cations of these elements. The decrease in the index of refraction derived from the replacement of oxygen by fluorine or hydroxyl is studied revealing the non-linear relation between their decrement in refractive index （D） and the volume ccupied by each oxygen （V0）, and the D-V0 curve of hydroxyl is defined by an analytical function expression. The effect of coordination number of cation on refractive index of mineral is also discussed. These relations may be applied to the works of structure analysis. The calculated and experimental m.r.i, of 37 minerals are compared, the largest deviation between the two is but ±0.008, and the average deviation is only ±0.0017.