Iterating density matrix

The density matrix is then reformed using the occupied set of eigenvectors, i.e., the lowest three levels. This yields:
 
Density Matrix (eV)
Atom 1 2 3 4 5 6
1 1.0000          
2 0.6667 1.0000        
3 0.0000 0.6667 1.0000      
4 -0.3333 0.0000 0.6667 1.0000    
5 0.0000 -0.3333 0.0000 0.6667 1.0000  
6 0.6667 0.0000 -0.3333 0.0000 0.6667 1.0000

Verify that the density matrix is correct.