[Q-e-developers] the sign of expression for force

[Jiqiang Li]

Dear all,
       Physically force can be denoted by F(R)= - dE/dR, and Helleman-Feyman theory is employed in DFT to evaluate force. In numerical routine of Pwscf code, does  force equal -dE/dR or dE/dR?

Jiqiang Li



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