[Pw_forum] Help on dipole and quadrupole moment!

[shangyi]

Dear all:
   I want to calculate the dipole and quadrupole moment of Ag atom when it adsorped on MgO slab using the one-side modle. How can I complete the calculation with pwscf? Though I examined the example 10 and searched the revelant information in maillist, I still have no ideas on it. 
   So I try the calculation with H atom adsorped on 5Layer Al slab, the steps are:
   1. relaxation the small system
   2. contiune the calculation with the keyword "nscf" "lberry" "gdir" and "nppstr".
I find it fails with information "Polarization is only for insulator and no empty band" if I using the "smearing" or the systme has odd electron. And it succeeds with even electron and "occupation=fixed". 
   The results is:
_______________________________________________________________________________________
           P =  -2.0127787  (mod  31.8198000)  (e/Omega).bohr
           P =  -0.0022491  (mod   0.0355556)  e/bohr^2
           P =  -0.1285842  (mod   2.0327730)  C/m^2
        The polarization direction is:  ( 0.00000 , 0.00000 , 1.00000 )
---------------------------------------------------------------------------------------
So I have three questions on the exercise:
    1. Are the results diople moment with different units?
    2. How can I get quadrupole moment?
    3. How can I do if the system has odd electron?
Any comments are appreciated!
Thanks in advance!
Best wishes!
shuix

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