This follows from the definition of Sass et al, J. Am. Chem. Soc. 1999, 121, 2047-2055,
http://dx.doi.org/10.1021/ja983887w.
The equations of (2) were converted using Gaussian elimination to obtain a reduced row echelon form,
so that the equations in terms of {A-2, A-1, A0, A1, A2} were derived. These have been coded into
the alignment tensor object calc_Am2, calc_Am1, calc_A0, calc_A1 and calc_A2 methods respectively,
and the values can be obtained by accessing the Am2, Am1, A0, A1, and A2 objects.
To check that the implementation is correct, a unit test has been created to compare the calculated
values with those determined using Pales.
