[QE-users] scf calculation of an amorphorse structure from md simulation coordinates

[Jayraj Anadani]

Dear QE community,

I have one particular molecular system of 10-20 atoms which I am getting
from a simulation of a large atom (around 10000 atoms) at a 300K
temperature from a molecular dynamic simulation (LAMMPS). and I also did
optimization of MD structure. now if i want to do DFT study to know the
bonding characteristic (i.e. DOS/PDOS) of atoms, at 300K configuration.what
is the best way to study dft.

I already did the AIMD/CPMD calculation using *cp.x* code but since my
material is amorphous metallic and CPMD is too delicate for metals and
couldn't control the kinetic energy of an electron (*ekin)*.
so,
1. Can I do direct SCF calculation(without relax) by giving a condition of
*forc_conv_thr* and *tot_conv_thr* with creating a vacuum(for a
non-periodic system) of around 15 Angstrom to converge properly. *OR*
2. I should do the RELAX calculation with vacuum and then go to the
*scf* calculation
to find the total energy and then *nscf*.

***questions:
1. what if I relax a system and position is changed a bit(which is obvious)
to minimize the total energy but that energy is at zero kelvin dft
calculation and I want to study the system at 300K. So how can small parts
of a structure reflect large MD simulation structural properties?

Thank you

Yours Sincerely,


Jayraj Anadani

Research Scholar
Department of Physics, Sardar Patel University

Gujarat, India-388120
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