The xxx.mat files provide the normalized eigendisplacements of OH stretching modes obtained by diagonalization of a partial dynamical matrix restricted to a single cluster of the hexagonal cell of dravite (see text). 

- Atoms are ordered as in the corresponding structure file xxx.cif. 
- Displacement coordinates are reported in a cartesian reference frame (X,Y,Z) defined such as the hexagonal lattice vectors are a=(1,0,0), b=(-1/2, sqrt(3)/2,0) c=(0,0,1). 
- Eigendisplacement coordinates should be multiplied by the square root of the corresponding atomic masses to obtain the eigenvectors.

