DFT: review U energies example

[certik]

John:

DFT ground state does not necessarily have 7s higher in energy than 6d. In fact, my featom code finds the following ground state energies/occupations for LDA (using Fermi-Dirac occupation with 0.001 Ha smear):

 Lowest eigenvalues and occupations (index, n, L, value, occupation):
    1:   1   0   -3.6889954761E+03    2.0000000000E+00
    2:   2   0   -6.3940729181E+02    2.0000000000E+00
    3:   2   1   -6.1874016342E+02    6.0000000000E+00
    4:   3   0   -1.6073349570E+02    2.0000000000E+00
    5:   3   1 -1.5059481296E+02    6.0000000000E+00
    6:   3   2   -1.3159427535E+02    1.0000000000E+01
    7:   4   0   -4.0152111179E+01    2.0000000000E+00
    8:   4   1   -3.5477394577E+01    6.0000000000E+00
    9:   4   2   -2.6747107088E+01    1.0000000000E+01
   10:   4   3   -1.4649108156E+01    1.4000000000E+01
   11:   5   0   -8.4639842362E+00    2.0000000000E+00
   12:   5   1   -6.6619644703E+00    6.0000000000E+00
   13:   5   2   -3.5226864132E+00    1.0000000000E+01
   14:   6   0   -1.1171982594E+00    2.0000000000E+00
   15:   6   1   -6.4359982973E-01    6.0000000000E+00
   16:   7   0   -9.8198270806E-02    1.2795018030E+00
   17:   5   3   -9.6948094138E-02    4.7204981970E+00
   18:   6   2   -5.8382915481E-02    0.0000000000E+00
   19:   7   1   -3.9951649510E-02    0.0000000000E+00
   20:   8   0   -3.2986444516E-03    0.0000000000E+00
   21:   8   1    3.3607509599E-03    0.0000000000E+00
   22:   9   0    5.0395456503E-03    0.0000000000E+00
   23:   7   2    5.7895441443E-03    0.0000000000E+00
 Difference of lowest 2 eigenvalues:   3.0495881843E+03
 Occupation-weighted eigenvalue sum:  -1.5774758217E+04