I am a new user of Quantum Espresso. I have to use Deuterium instead of Hydrogen for my work in DFT studies. Hydrogen Pseudopotential file is available in QE website. Please clarify what parameters I have to set in the QE input file in order to simulate Deuterium in QE.
The main difference between deuterium and hydrogen is the mass, so you need to set the mass of the "hydrogen" so that it matches deuterium. I'm not a Quantum Espresso expert, but I think you do this by setting the
ATOMIC_SPECIES card, see:
However, you need to be clear about what effects you are wanting to simulate, because many common simulation tasks are not affected by the nuclear mass at all.
The pseudopotential doesn't care about the nuclear mass, so you don't need to change anything. For the same reason, the electronic ground state will be identical between hydrogen and deuterium, since Quantum Espresso uses an adiabatic approximation to decouple the nuclear and electronic wavefunctions. If you look at the "electronic" Kohn-Sham equations, the nuclear mass doesn't appear at all.
The optimised geometry of your material or molecule will also be the same; this is because Quantum Espresso optimises the structure at zero Kelvin and treats the atoms semi-classically, so there is no quantum delocalisation/zero-point motion for the nuclei - essentially, there is no nuclear kinetic energy term. If there is no temperature and no nuclear quantum effects, then the nuclear mass doesn't enter any of the equations and deuterium will give the same answer as hydrogen.
The mass will affect molecular dynamics and path-integral/ring-polymer molecular dynamics, and it will also affect any vibrational properties such as phonons (though the force constant matrix will be the same as for hydrogen). Other nuclear properties might be relevant for some kinds of simulations, such as the nuclear spin (e.g. for NMR chemical shifts).