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点发散单色x-射线在单晶中衍射的消光吸收线构成吸收锥。吸收锥与参考球的截线是吸收圆。若三个倒易结点F(h_F,k_F,l_F)、I(h_I,h_I,l_I)、C(h_C,k_C,l_C)的吸收圆构成三圆交点型透镜(指透镜的长度为第三个吸收圆的直径者),则该透镜所相应的三个平面的交点C(x,y,z)是第三个倒易结点C(h_C,k_C,l_C)。对任何透镜(二圆或三圆交点型透镜),都能求出相应的三个平面的交点,若求出的交点C(x,y,z)的座标数x、y、z不全为整数,则该交点可视为代表不能衍射的虚晶面族(xyz)。此时的透镜为二圆交点型透镜,不存在以透镜长度为直径的第三个吸收圆。在模型球面上的吸收圆花样中,很容易找到长度短的二圆交点型透镜,亦即很容易找到小ф的虚晶面族的吸收锥,因此用虚晶面可求得高精度的点阵参数。本文的计算实例为:先选二圆交点型透镜求出相应的虚晶面族,然后解出点阵参数。用虚晶面求得GaAs单晶的α±σ=5.653436±0.000032A,Δα/α=1.13×10~(-5)。
Dichroic monochromatic x-ray diffraction in the single crystal diffraction absorbing absorption absorption cone forming the cone. Absorption cone and reference ball cross-section is the absorption circle. If the absorption circles of the three reciprocal nodes F (h_F, k_F, l_F), I (h_I, h_I, l_I) and C (h_C, k_C, l_C) form a triple circle intersection type lens ), The intersection C (x, y, z) of the corresponding three planes of the lens is the third reciprocal node C (h_C, k_C, l_C). For any lens (two-circle or three-circle intersection type lens), the intersection points of the corresponding three planes can be obtained. If the coordinates x, y, z of the intersection point C (x, y, z) Integer, then the point of intersection can be regarded as representing a group of xyz that can not be diffracted. The lens at this time is a two-circle intersection type lens, and there is no third absorption circle having the lens length as a diameter. In the absorption pattern on the spherical surface of the model, it is easy to find the short circular two-circular intersection lens, that is, it is easy to find the absorption cone of a small ф imaginary crystal family, so the point with high precision can be obtained by using the virtual crystal plane Array parameters. The calculation example in this paper is as follows: First, choose the two-circle intersection lens to find the corresponding imaginary plane family, and then solve the lattice parameters. Α ± σ = 5.653436 ± 0.000032A and Δα / α = 1.13 × 10 -5 of GaAs single crystal were obtained by using the virtual crystal plane.