Dear Sir,
*your structure is not exactly cubic* (look at your atoms position).
> I wonder why you use atomic coordinate which looks like
> the result of relaxation along with lattice parameters
> which look like given by hand. Relax either both, or none.
>
1) i relaxed both atomic coordinates and lattice parameters using variable
cell option and got
outcoor: Relaxed atomic coordinates (scaled):
0.00005993 0.00006110 0.00005744 1 Mg 1
0.48553111 0.48553523 0.48553182 2 O 2
outcell: Unit cell vectors (Ang):
-0.000022 2.044803 2.044814
2.044808 -0.000026 2.044818
2.044803 2.044802 -0.000021
so i used lattice constant=4.089606~4.09 Ang.
2) when i did study of energy v/s volume, i got minima at 4.10 Ang, with out
above relaxation.
should i proceed this way, keeping care of symmetry or should i see the
final results(freqs) to decide, which one to use (relaxation or no
relaxation)?
3) can we use macroscopic polarisation analysis for small band gap
materials? sorry, if my question is stupid.
With Due Regards,
Sonu Kumar
Phd Student
Indian Institute of Technology Delhi
Delhi-110016
web:-http://www.iitd.ac.in/
