:orphan:


Converging atoms
================

DIRAC presently does not perform an open-shell Hartree--Fock in a strict sense,
rather an average-of-configuration calculation, which amounts to the
optimization of the average energy of a set of configurations (or determinants)
generated from the specification of a given number of open shells and their
electron occupations. In the case of atoms, a convergence problem can occur when
the inner open-shell orbitals are more stable than outer "closed" shell.
From DIRAC21 onwards, we have atomic supersymmetry and can specify the occupation number of each :math:`\kappa` value. by using the keyword :ref:`SCF_.KPSELE`. 

As examples of such calculations, we consider the Nb and Np atoms.

-----------------------------------------------------
Example 1:  Nb [Kr]4d\ :sup:`4`\ 5s\ :sup:`1`\
-----------------------------------------------------
::

  **DIRAC
  .WAVE FUNCTION
  .ANALYZE
  **HAMILTONIAN
  .X2C
  **INTEGRALS
  *READIN
  .UNCONTRACT
  **WAVE FUNCTION
  .SCF
  *SCF
  .CLOSED SHELL
   18 18
  .OPEN SHELL
   2
   4/10,0
   1/2,0
  .KPSELE                                                                                             
   5                                                                                                   
   -1  1 -2  2 -3                                                                                      
    8  6 12  4  6                                                                                      
    0  0  0  4  6                                                                                      
    2  0  0  0  0   
  **ANALYZE
  .MULPOP
  *MULPOP
  .VECPOP
   1..oo
   1..oo
  *END OF

----------------------------------------------------------
Example 2:  Np [Rn]5f\ :sup:`4`\6d\ :sup:`1`\7s\ :sup:`2`\
----------------------------------------------------------
::

  **DIRAC                                                                                             
  .WAVE FUNCTION                                                                                      
  .ANALYZE                                                                                            
  **HAMILTONIAN                                                                                       
  .X2C                                                                                                
  **INTEGRALS                                                                                     
  *READIN                                                                                             
  .UNCONTRACT                                                                                         
  **WAVE FUNCTION                                                                                     
  .SCF                                                                                                
  *SCF                                                                                                
  .CLOSED SHELL                                                                                       
   44 44                                                                                              
  .OPEN SHELL                                                                                         
  2                                                                                                   
  4/0,14                                                                                              
  1/10,0                                                                                              
  .KPSELE                                                                                             
  7                                                                                                   
  -1  1  -2  2 -3  3 -4                                                                               
  14 10  20 12 18  6  8                                                                               
   0  0   0  0  0  6  8                                                                               
   0  0   0  4  6  0  0                                                                               
  **ANALYZE                                                                                           
  .MULPOP                                                                                             
  *MULPOP                                                                                             
  .VECPOP                                                                                             
   1..oo                                                                                              
   1..oo                                                                                              
  *END OF