> We are very interested in knowing whether there is a program that will
>take x-ray parameters (bond lengths, angles, space group, etc) for
>solids such as intercalated vanadium oxides and calculate the expected
>infra-red spectrum.
... me, too !
I don't think there is any, but if so, I would like to get the hint as well.
Several problems are related with such a program:
1) Crystallographic info is not sufficient in this case. In fact,
additional information will be necessary on the force constants of the
bonds, at least between next neighbour atoms.
2) Allthough there is software to calculate (and visualize) the possible
lattice deformations (vibration modes) and algorithms for the factor-group
analysis exist, there remains a problem, since the deformations are rather
easily expressible in 3D coordinates (where we have the symmetry operations
e.g. from the International Tables), but force constants are most easily
expressed in terms of the so called internal coordinates, the directions of
the bonds (1D !).
3) This is not all of the job, since macroscopic effects have not yet been
a part of the discussion. The method used to take the spectra (transmission
or reflection) has heavy influence on the shape of the absorption bands. In
case of diffuse reflectance for example the macroscopic properties of the
sample will be of influence (particle size etc. viz. Kubelka-Munk theory).
Usually the difficult part of such a program consists of the calculation of
the vibration energies from the atomistic model of the molecule/solid. But
the use of all this is questionable, because people are usually satisfied,
when they have the spectrum. They don't want to know about the details. ;-/
Carsten
Carsten Schinzer ---------------------------------------
Institut de Chimie de la Matiere Condensee de Bordeaux
87, Avenue du Docteur A. Schweitzer
F-33608 PESSAC
fon +33 556 84 2650 (poste 7397) fax +33 556 84 2640
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