[QE-users] How H2O molecule reflect DFT scf calculation at 0 Kelvin calculation

[Jayraj Anadani]

Dear QE
              I put H2O molecular atoms small far apart from each other
within large supercell so that the periodic image of the H2O do not
interact with each other and run a scf calculation my convergence done
successfully with good amount of accuracy upto 10^-9. But it is not
reflecting original H2O molecule at 300 Kelvin...but when i relaxing these
atoms and then did scf calculation they are reflecting H2O at 300k by
observing bond angel and length.. how ? And my question is
1) scf is also doing calculation using iteration method algorithm by using
electronic densities at ground state so why they converge when two hydrogen
atoms and one oxygen atom are not at appropriate distance.still scf
converge how ?
2) also by doing relax calculation all of sudden two hydrogen and one
oxygen come closer and they formed a bond and bond angel which is reflect
300k H2O molecule structure. So how two hydrogen and one oxygen atoms knows
during relaxation that i have to make structure at a room temperature?


Thank you
Regards

JAYRAJ ANADANI
Ph.D Research scholar
Department of physics
Sardar Patel University
Anand,Gujarat,
India
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