The ABINIT Users Mailing List ( CLOSED )

["D. R. Hamann" <drhamann@mat-simresearch.com>]

Dear Jian,

Abinit can calculate the elastic tensor directly, giving the results in 
Cartesian coordinates and standard units (GPa).  Work through the 
tutorial "elastic properties" and you should be able to apply these 
methods to your problem.  (If you haven't done so, be sure to work 
through the basic tutorials first.)

From your questions, it sounds as if you intended to calculate the 
elastic constants by numerical differentiation.  This is very tricky, 
and it is very difficult to get accurate results this way, especially 
for any structure with internal degrees of freedom.

Don Hamann

Z.J. wrote:
> Hi, dear all users,
>       I am so sorry to disturb you. I have some problems 
> about the elastic constants calculations to turn to you for your 
> help.My problems are as follows:
>      (1) Must the strain matrix be multiplied with the vector of the
> primitive cell? If the strain matrix multiplies with the conventional
> lattice vectors, could I obtain the right calculation results?
>      (2) Will both the Cartesian coordinates and the fractional (x,y,z) of
> atoms in the distorted primitive cell change after distortation? If they
> will change, how and what will they change?
>      (3) How to determine the space group of distorted primitive cell? 
>
>      In all, the key point of the problem is how to obtain the input 
> data of
> distorted lattice of crystal.
>
>      Thank you for your valuable and informative advice very much.
>
>      Best regards.
>
>     Yours sincerely,
>
>                                                Jian Zhu 

--
D. R. Hamann
Mat-Sim Research LLC    | Deptartment of Physics
P.O. Box 742            |  and Astronomy
Murray Hill, NJ 07974   | Rutgers University
phone: 908-370-8079     | 732-445-4381

email: drhamann@mat-simresearch.com