[Pw_forum] maybe a bug in the QE 4.0.4 (Paolo Umari)

[umari at democritos.it]

Dear Hanghui,

> I did the test to check the forces and stress in the Berry phase
> method with the ultrasoft pseudopotential. The forces are correct but the
> stress is around 50% smaller. I am not sure whether it is due to the
> ultrasoft pseudopotential or not.

At this moment, With a finite electric field, the forces are calculated
correctly also with ultrasoft pseudopotentials. However, this is not the
case of stress, which is calculated correctly only for normconserving
pseudopotentials. The US case requires an extra term for the stress 
which we  still have to implement.

Best regards,

Paolo Umari (Democritos)


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