Dear Seitaro Yazawa, > Even though I’ve set the target pressure to 0 GPa for 2000 steps, the > time-averaged pressure over > several thousand steps stays about 0.5 GPa lower than expected. I also > checked using a moving
In general, the fluctuation of the pressure, say, plus or minus 0.5 GPa, is normal in finite temperature molecular dynamics simulations as the ‘virial’ is used to derive the macroscopic pressure from the atomistic forces. Imagine that the 80 atoms moving correspond to the temperature of 300 K, and recording their movement every femtosecond. The fluctuations of microscopic forces directly affect the calculated instantaneous ‘virial’ pressure. > So far, I’ve tried several approaches to reduce Pulay stress and improve > pressure convergence: > Increased the plane-wave cutoff energy to 80 Ry Instead, decrease the setting temperature to 50 K and calculate the system for an extended period, such as 100000 steps, to see if it achieves the desired pressure. Sincerely yours, 西館数芽 Kazume NISHIDATE Ph.D Department of Systems Innovation Engineering, Graduate School of Science and Engineering, Iwate University 4-3-5 Ueda, Morioka, Iwate, 020-8551 JAPAN Phone:+81-19-621-6391 [email protected], [email protected] https://sites.google.com/site/nisidatelab/ _______________________________________________________________________________ The Quantum ESPRESSO Foundation stands in solidarity with all civilians worldwide who are victims of terrorism, military aggression, and indiscriminate warfare. -------------------------------------------------------------------------------- Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
