Indeed, since your XRD experiment is not a theta-two theta experiment but a detector scan (with a fixed grazing incidence angle), you are not able to measure any texture except if the diffraction vector stands along the texture direction which is roughly your case, by chance. I have calculated that the angle between the diffraction vector direction for the (002) diffraction peak and the normal of the sample surface is around 14° (assuming a 3° grazing angle).

有高手给解释一下那个14度是怎么计算的吗？或者给点提醒，谢谢阿，跪谢