[Pw_forum] The quantity of displacement for atom position in example 10

[Q.J.Wang]

Dear all
Example 10 shows how to calculate the polarization by berry phase, but I have a problem about it, that is how to selecte the quantity of displacement for Pb atom. In this example, the displacement of Pb in Z direction is 0.01 in fractional coordinate. It is known that the polarization value is depended on the quantity of displacement, so which displacement is correct in calculated the polarization value? how to select? 
Any suggestion is appreciated.


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Best regards
 
Q.J.Wang
 
Yunnan Normal University
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