[Pw_forum] Force calculation time in relaxation under electric field

[Mostafa Youssef]

Dear all,


I performed ionic relaxation for 3x3x3 unit cells of a semiconducting oxide under electric field (lelfield =.true.) using ultrasoft PP and 1x1x3 MP K-point grid where 3 is in the direction of the electric field. These are GGA+U calculations. I noticed in the time report that force calculations time is becoming even more than the electrons time as shown below:

     init_run     :      8.32s CPU      8.91s WALL (       1 calls)
     electrons    :  42723.25s CPU  44995.21s WALL (       5 calls)
     update_pot   :      2.62s CPU      3.19s WALL (       4 calls)
     forces       :  66735.95s CPU  66943.64s WALL (       5 calls)

This is first time in which I find PWscf use more time in force calculations than in electrons. For the same system and without electric field , forces time would be about 0.2 of electrons time.  Is this a normal behavior and is there a recommended possibility to reduce force calculation time?

I attempted using Norm Conserving PP's but unfortunately I could not get the code pass the 1 ionic step because of the S matrix not being positive definite.

I appreciate your thoughts on this.

Regards,
Mostafa Youssef
MIT

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