The Crystal Chemistry of the Silicate Garnets
The Crystal Chemistry of the Silicate Garnets
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DOI：
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发表时间：
1971-06
影响因子：
3.1
通讯作者：
G. Novak;G. V. Gibbs
中科院分区：
文献类型：
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作者：
G. Novak;G. V. Gibbs
精制结构的8个天然石榴石[铬镁铝榴石，铁铝榴石，spessartine，Mngrossular，grossular，uvarovite，goldmanite，和钙铁榴石]与合成镁铝榴石，以确定多面体的相互作用，键长和角度的取代基阳离子的影响进行了比较。这些石榴石中的Si-O键构成了两个种群，它们可以与（r！X！），X十二面体阳离子的平均半径。如果（r{X}）小于1.0 A，则Si-O= 1.635：1：0.005 A，但如果（r！X1）超过1.0 A，则Si-O = 1.650至.005 A。而X-O和Y-O键长以及O-X-O、O-Y-O和O-Si-O角与（r{X！）和（r[Y]）（其中（r[Y]）= Y八面体阳离子的平均半径）。多元线性回归分析表明，这些石榴石的位置参数与（1 ′ {X}）和（1 ′ [V]）有关，使用Shannon和Prewitt的有效半径如下：x = 0.006 + 0.022（r{X}）+ 0.014（r[Y]）y = 0.051 - 0.023（r{X}）+ 0.037（r[Y]）z = 0.643 - 0.009（r{X}）+ 0.034（r[Y]）。用这些方程[x=0.0336; y =0.0491; z=0.6530]计算的Fe-镁铝榴石的位置参数与观测值[x=0.0339（5）; y =0.0491（6）;z=0.6535（6）]（Euler和布鲁斯，1965）在统计上一致。此外，用56个表征良好的硅酸盐石榴石的回归方程[a=9.04+1.61（r{XD+1.89（r[YJ]）]]计算晶胞边缘，预测的位置参数给出的键长和键角与观测值在统计学上一致。这些方程用于预测200多种假设的立方硅酸盐石榴子石化合物的结构细节，方法是将（r{XI）值指定为0.80至1.50 A之间，将（r[Y]）值指定为0.50至1.15 A之间（间隔为0.05 A）。使用基于合理的0-0、Si-O、X-O和Y-O距离的标准，绘制了一个图，其中硅酸盐石榴石的结构“稳定性”场被描绘为（r{X}）和（r[Y]）的函数。
Refined structures of eight natural garnets [Cr-pyrope, almandine, spessartine, Mngrossular, grossular, uvarovite, goldmanite, and andradite] are compared with that of synthetic pyrope to determine the effects of the substituent cations on polyhedral interactions,bond lengths, and angles. The Si-O bonds in these garnets constitute two populations whichcan be related to (r!X!), the mean radius of the X dodecahedra] cation. If (r{X}) is lessthan 1.0 A, then Si-O= 1.635 :1:0.005A, but if (r!X\) exceeds 1.0 A, then Si-O = 1.650 to.005 A. However, the X-O and Y-O bond lengths and the O-X-O, O-Y-O, and O-Si-O anglesare linearly dependent on (r{X!) and on (r[Y]) (where (r[Y])= the mean radius of the Y octahedral cation). A multiple linear regression analysis indicates the positional parameters of these garnets to be related to (1'{X} ) and (1'[ V]) using Shannon and Prewitt's effectiveradii as follows: x = 0.006 + 0.022(r{X} > + 0.014(r[Y]) y = 0.051 - 0.023(r{X}) + 0.037(r[Y]) z = 0.643 - 0.009(r{X}) + 0.034(r[Y]). The positional parameters of Fe-pyrope calculated with these equations [x=0.0336; y =0.0491; z=0.6530] are in statistical agreement with the observed [x=0.0339(5); y =0.0491(6);z=0.6535(6)] (Euler and Bruce, 1965). Furthermore, using a cell edge calculated from an equation obtained by regression analysis of 56 well characterized silicate garnets [a=9.04+1.61(r{XD+1.89(r[YJ)], the predicted positional parameters give bond lengthsand angles that are statistically identical with those observed. These equations were used to predict the structural details of over 200 hypothetical cubic silicate garnet compounds by assigning (r{XI) values between 0.80 and 1.50 A and (r[Y]) values between 0.50 and 1.15 A (at 0.05 A intervals). Using criteria based on reasonable 0-0, Si-O, X-O, and Y-O distances, a diagram was prepared in which the structural "stability" field of silicate garnets is delineated as a function of (r{X}) and (r[Y]).