The displacement parameters , , and , given by eqs. (2.1.22), (2.1.25), and (2.1.26), are so closely related that the use of all of them in the crystallographic literature is not only unnecessary, but conducive to confusion. The relationships needed are shown in a single equation, obtained by comparison of eqs. (2.1.21), (2.1.24) and (2.1.27):

It is true
that fewer arithmetic operations are needed to compute *T* from
than from , but with the advent of computers this
advantage has become negligible.