Convert rank-2 cartesian tensor to spherical tensors

[T0,T1,T2] = tensor_cart2sph(Tc)

This function takes as input Tc a rank-2 cartesian tensor represented by a 3x3 matrix. It returns the corresponding rank-0, rank-1, and rank-2 irreducible spherical tensors in T0 (a scalar), T1 (a 3x1 array), and T2 (a 5x1 array).

Calculate the spherical tensors corresponding to a rhombig g matrix:

g = diag([2 2.1 2.4]);
[g0,g1,g2] = tensor_cart2sph(g)

g0 =
    -3.7528
g1 =
   0
   0
   0
g2 =
      -0.05
          0
    0.28577
          0
      -0.05    

isto, tensor_sph2cart