File Applications/SpinW/m_files/sw_basismat.m

  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.