Option LATTDR specifies that the
``Lattice Dispersion Relation'' of Draine and Goodman (1993)
be employed to determine the
dipole polarizabilities.; other possible choices are DRAI88 (prescription
used by Draine 1988) and GOBR88
(prescription used by Goedecke & O'Brien 1988
and Hage & Greenberg 1990).
In the limit 
(where 
is the wave
vector and d is the lattice spacing) all three options converge to the same
limit; for |m|kd > 0.1
there are significant differences among them. Consult
the paper by Draine & Goodman (1993) for
discussion and comparison of these
three prescriptions.
Option LATTDR is recommended for general use,
based upon the tests presented by Draine & Goodman (1993).