Hello QE users: I want to do calculations for the systems in the finite electric field, just similar to example30. However, when I tested the example30, I found some problems. 1. When I use the input file ?mgo.cp.cg.efield.in? to calculate the system?s properties keeping the position of the atoms fixed in the experimental equilibrium positions in the presence of an electric field E of 0.001 a. u. along the 3rd direction, the forces on the atoms are difference from those in ?/emample30/reference/mgo.cp.cg.efield.out?. For the calculated results (should be found in the ?/tmp/mgo.for? file), the force on Mg atom in the z direction is 0.1955E-02 a.u., which is almost the same at that in ?/emample30/reference/mgo.cp.cg.efield.out?, whereas the force on O atom in the z direction is -0.1096E-02 a.u., which is about half of that in ?/emample30/reference/mgo.cp.cg.efield.out?. The forces on Mg and O atoms in the z direction are 0.1955E-02 and -0.2040E-02 a.u. in ?/emample30/reference/mgo.cp.cg.efield.out?. So, I just want to know why there is so large difference between the calculated results and the reference results. 2. Another problem is that the masses of O atom in ?mgo.cp.cg.in?, ?mgo.cp.cg.efield.in?, ?mgo.cp.damp.efield.in? are 12.01, 12.01, and 1, respectively. Is that wrong? I would appreciate if someone can response for this.
Regards, Xu Bo
