[Pw_forum] stable phase

[Mike Mehl]

If you found a phonon with an imaginary frequency, then you can find a 
supercell of the L10 structure, displace the atoms in it according to 
the symmetry of the phonon, and relax the structure to obtain another 
structure with lower energy (enthalpy if you are working at fixed 
pressure).  Here's how I did it:

Michael J. Mehl, Gus L. W. Hart and Stefano Curtarolo
Density functional study of the L10–αIrV transition in IrV and RhV
Journal of Alloys and Compounds
Volume 509, Issue 3, 21 January 2011, Pages 560-567
http://dx.doi.org/10.1016/j.jallcom.2010.08.102

Note that the instabilities we found in the IrV L10 structure will not 
necessarily be the same as you find in L10 M-C.

On 09/22/2011 01:30 PM, bhabya sahoo wrote:
> i am calulated  b1 to b2 transition of some metal carbide
> i found b1 to b2 transition at 140 gpa
> from phonon dispersion i found dyanamical unstabilty at 140 gpa b1 phase
> but i am also
> found b2 is dyanamical unstable(in X and M) directions so i thought
> there must be other phase which may be stable at 140 gpa
> for this calculated L10 phase which will less enthalpy than b2 at 140
> gpa but also this shows imaginary frequency  in X  direction
> so what is the stable phase?
>
> b d sahoo barc
> mumbai
>



-- 
Michael J. Mehl
Head, Center for Computational Materials Science
Naval Research Laboratory Code 6390
Washington DC