Some notation to be used in this report for basis vectors
and their components is summarized here. The local instantaneous
atomic position vector is denoted by r+u, with
r the mean atomic position vector and u the displacement
vector of an atom from its mean position. We use the symbols 
, and 
, as is common, for the lengths of the reciprocal axes.
Quantities referred to the direct lattice basis, a,
b, c (or equivalently 
)
:
Components of r: x, y, z (or equivalently 
).
Components of u: 
(or
equivalently 
).
Related anisotropic displacement parameter: 
; (dimensionless).
Quantities referred to the basis 
(or equivalently 
):
Components of r: 
(or equivalently 
).
Components of u: 
(or
equivalently 
).
Related anisotropic displacement parameter:
; (length)2 .
Quantities referred to the Cartesian basis 
):
Components of r: 
(or
equivalently 
).
Components of u: 
(or equivalently 
).
Related anisotropic displacement parameter: 
;
(length)2 .