Soc hgh performaces
Using the analytical expression S = LzSz + 1/2( L_+S_- + L_-S_+ ) to compute the spin-orbit part for the HGH pseudopotentials in a much more efficient way. Complex spherical harmonics must be used instead of the real one to compute analytically the operation of L to projectors. The memory usage is also reduced.
The routines is checked to be faster for a wide range of grid points in batches (17000 to 650000) and the gain is over 2 for the entire range.