[Pw_forum] phonons

[bothina hamad]

Dear users,
                    
I am starting phonon calculations of a full Heusler alloy ( 4 atoms per unit 
cell). The alloy is  half-metallic (metallic in majority spin channel and 
semiconducting in the minority). It is also a ferromagnet with a total magnetic 
moment 2 Bohr magnetons. 


Using a small grid  2x2x2, I got the phonon calculations working smoothly and I 
got the phonon density of states. However, I could not  reach convergence for 
denser grids. In these calculations, I then tried to split the points and make 
calculations for each q point in the grid separately, I found the the 
convergence occur for the 3 q-points ( the same points as 2x2x2 grid), however 
no  convergence is reached for the other point and the calculations keep 
oscillating
until 100 iterations then stop. I tried to change some parameters such as 
decreasing the tr2_ph=1.0d-14 to tr2_ph=1.0d-18, and also 

by decreasing the mixing to 0.1, still the problem is not solved.


I use espresso-4.2.1 version 

I attach the input of scf and phonon calculations, dyn0 file  as well as the 
last part of the output for the second q point after which the calculations 
stop.

Do you have  any idea that can solve the problem

Best wishes

Dr. Bothina Hamad
Physics Department
University of Jordan
Amman-11942, Jordan
Tel:  +962-6-5355000
ext#22030 & 22023
Fax:+962-6-5348932
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