[QE-users] Which celldm(i) to choose for DOS

[Sudip Kumar Mondal]

Hi all ,

I'm currently using QE 5.4.0. & I have a general question regarding the
calculation of density of states (LDOS & PDOS).

Before estimating any physical observable we optimize (relax/vc-relax or
sometimes both) the structure in hand to obtain accurate lattice
parameter(s) corresponding to zero kBar pressure. Optimizations w.r.t. all
other parameters (k-point grid , ecutwfc , ecutrho etc.)  are also
performed.
However for a single scf run with the lattice parameter(s) corresponding to
zero pressure as obtained from relax/vc-relax , yields some different
pressure other than zero kBar.  In my case then I ran a series of single
scf calculations for converging to zero pressure by varying the lattice
parameter. The scf convergence to zero pressure was successful. But the
lattice parameter  turned out be smaller than its zero pressure equivalent
obtained from relaxation by ~ 0.9 bohr.

Now, my question is whether I should proceed to calculate DOS with the
value of the lattice parameter(s) corresponding to zero pressure obtained
from relaxation or with the same obtained from the series of single scfs?


Regards.
-- 
Sudip Kumar Mondal
DST INSPIRE Fellow
High Pressure & Temperature Laboratory
Dept. Of Physics/Geological Sc.
Jadavpur University.
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