iFit/sw_basismat

 determines allowed tensor components in a given point group symmetry

 [M, asym] = SW_BASISMAT(symOp, r, tol) 

 It determines the allowed matrix elements compatible with a given point
 group symmetry. The matrix can describe exchange interaction or single
 ion anisotropy.

 Input:
 symOp     Generators of the point group symmetry, dimensions are
           [3 3 nSym]. Each symOp(:,:,ii) matrix defines a rotation.
 r         Distance vector between the two interacting atoms. For
           anisotropy r=0, dimensions are [3 1].
 tol       Tolerance, optional. Default value is 1e-5.

 Output:

 M         Matrices, that span out the vector space of the symmetry
           allowed matrices, dimensions are [3 3 nM]. Any matrix is
           allowed that can be expressed as a linear combination of the
           symmetry allowed matrices.
 asym      Logical vector, for each 3x3 matrix in M, tells whether it is
           antisymmetric, dimensions are [1 nM].

 See also SW.GETMATRIX, SW.SETMATRIX.