[Pw_forum] Something strange in the calculation with the spin=2 and multiplicity=1

[vega lew]

Dear all

I have compare the results of two calculation for singlet state with or 
without the option 'spin=2, multiplicity=1'.

I used to think the calculation with the option 'spin=1' by default was 
the singlet state of the system and the calculation with the option 
'spin=2, multiplicity=1' was also the same calculation for the singlet 
state as the default setting.

But comparing the results given by the two calculation with or without 
the option 'spin=2, multiplicity=1', we find the calculated energy is a 
little different. Calculation for singlet state with 'spin=2, 
multiplicity=1' reported the energy was -88.6587995084 Ry. On the 
contrast, the calculation without the 'spin=2, multiplicity=1' reported 
that the energy was  -88.6595028258 Ry.
By the way, the threshold for the scf or relax calculation is setting as 
default value of QE 4.1.2
I wondering whether the both energy is reasonable for the singlet? Why 
the turn out to be different?

thank you for reading.

best

vega
-- 

==================================================================================
Vega Lew ( weijia liu)
Graduate students
State Key Laboratory of Materials-oriented Chemical Engineering
Nanjing University of Technology, 210009, Nanjing, Jiangsu, China
***********************************************************************************************
Email: vegalew at gmail.com
Office: Room A705, Technical Innovation Building, Xinmofan Road 5#, 
Nanjing, Jiangsu, China
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