Thank you for your response. On Wed, Oct 18, 2023 at 6:59 PM Kazume NISHIDATE <[email protected]> wrote:
> Dear Jayraj; > > > the temperature fluctuations are too high compared to the other > > literature. > > Because you are using "thousands of atoms" in LAMMPS while you are using > only the 128 atoms in QE. > > > MD simulation of thousands of atoms in LAMMPS > ……. > > On my metallic system, which has 128 atoms, > > > You must understand the concept of ensemble average. > A good text was introduced by Nicola: > > > 3) not sure where to start - you need to learn and understand MD - a > > good start is if you google "ercolessi md primer" > > > In addition to his elemental comments, I want to add some trivial > things. > > > "conv_thr" (i.e. ecutwfc=5 or 10) below a minimum cutoff of > > pseudopotential? So that I can get the next ionic position very > > Suppose you have a potential curvature having a shape like a cup and > a ball is falling along its curvature from its edge. The ball will > perform oscillating behavior continually if there is no energy loss by > a friction (energy conservation). > > In a primitive molecular dynamics calculation (MD), total energy > (kinetic+potential) must be preserved in the long time scale (say > 10000 time steps) when the system does not have a restriction on its > kinetics (like temperature regulation). > > The "ecutwfc=5" apparently insufficient to evaluate the potential > curvature and hence your MD calculation will collapse. It is > equivalent to a MD in LAMMPS with random interaction potentials. > > Use the default cutoff energy and monitor the fluctuation of total > energies in the MD runs with changing the dt (time increment value) to > find the appropriate (largest) dt with preserving the total energies. > > And you can also consider a gamma-point only calculation if your > system is large enough. > > > > 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 community stands by the Ukrainian > people and expresses its concerns about the devastating > effects that the Russian military offensive has on their > country and on the free and peaceful scientific, cultural, > and economic cooperation amongst peoples > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
