              The [2][3] element of the 3x3 matrix used to transform Cartesian\
               coordinates in the ATOM_SITE category to fractional coordinates\
               in the same category. The axial alignments of this\
               transformation are described in _atom_sites.Cartn_transform_axes.\
               The 3x1 translation is defined in\
               _atom_sites.fract_transf_vector[].\
\
               |x'|               |11 12 13| |x|              |1|\
               |y'|~fractional~ = |21 22 23| |y|~Cartesian~ + |2|\
               |z'|               |31 32 33| |z|              |3|