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Re: [abinit-forum] question abou the unit of rigid-atom elastic tensor in output file, Ha/(a.u.^3) or orther?

From: "D. R. Hamann" <drh@bell-labs.com>
To: forum@abinit.org
Subject: Re: [abinit-forum] question abou the unit of rigid-atom elastic tensor in output file, Ha/(a.u.^3) or orther?
Date: Mon, 28 Mar 2005 13:36:00 -0500

Dear Zhufeng,

The units are Hartree/Bohr^3. To convert to GPa, multiply by 2.9421E+4. In general, users are expected to use anaddb after doing a response-function abinit run, which will do the conversion, output the elastic tensor in the 6X6 form you have below, and take atomic relaxation corrections into account. See the anaddb help file, especially the elaflag input variable. Also see Test_v4/t66.in to t70.in (and the README file) for examples. Also take a look at Infos/Theory/vanderbilt-anaddb-notes.pdf.

The translation between the Voigt strain indices and the Abinit perturbation indexing is as follows:

Voigt dir pert

1 1 natom+3
2 2 natom+3
3 3 natom+3
4 1 natom+4
5 2 natom+4
6 6 natom+4

I've labeled your output with the three inequivalent C elements for cubic symmetry.

Regards,
Don Hamann

zfhou@mail.edu.cn wrote:

Dear abinit users,

I have tested to calculate the strain pertubations of strain type for
Silicon(diamond structure) and got the output file. Now I have some question
about the rigid-atom elastic tensor.
1. What is the unit of rigid-atom elastic tensor?
2. How to map the the following data to the C11, C12, C44 of cubic Silicon?
I know the elastic tensor of cubic crystal can be written the following 6x6
matrix:
{C11 C12 C12 }
{C12 C11 C12 }
C= {C12 C12 C11 }
{ C44 }
{ C44 }
{ C44 }

Thanks for your kind help!
Regards
zhufeng

--------My calculated output file:----------------------------
Rigid-atom elastic tensor , in cartesian coordinates,
j1 j2 matrix element
dir pert dir pert real part imaginary part
1 5 1 5 0.0082516915 0.0000000000 C11
1 5 2 5 0.0048080107 0.0000000000 C12
1 5 3 5 0.0048080107 0.0000000000
1 5 1 6 0.0000000000 0.0000000000
1 5 2 6 0.0000000000 0.0000000000
1 5 3 6 0.0000000000 0.0000000000
2 5 1 5 0.0048080097 0.0000000000
2 5 2 5 0.0082516959 0.0000000000
2 5 3 5 0.0048080107 0.0000000000
2 5 1 6 0.0000000000 0.0000000000
2 5 2 6 0.0000000000 0.0000000000
2 5 3 6 0.0000000000 0.0000000000
3 5 1 5 0.0048080097 0.0000000000
3 5 2 5 0.0048080107 0.0000000000
3 5 3 5 0.0082516958 0.0000000000
3 5 1 6 0.0000000000 0.0000000000
3 5 2 6 0.0000000000 0.0000000000
3 5 3 6 0.0000000000 0.0000000000
1 6 1 5 0.0000000000 0.0000000000
1 6 2 5 0.0000000000 0.0000000000
1 6 3 5 0.0000000000 0.0000000000
1 6 1 6 0.0062890190 0.0000000000 C44
1 6 2 6 0.0000000000 0.0000000000
1 6 3 6 0.0000000000 0.0000000000

2 6 1 5 0.0000000000 0.0000000000
2 6 2 5 0.0000000000 0.0000000000
2 6 3 5 0.0000000000 0.0000000000
2 6 1 6 0.0000000000 0.0000000000
2 6 2 6 0.0062890126 0.0000000000
2 6 3 6 0.0000000000 0.0000000000
3 6 1 5 0.0000000000 0.0000000000
3 6 2 5 0.0000000000 0.0000000000
3 6 3 5 0.0000000000 0.0000000000
3 6 1 6 0.0000000000 0.0000000000
3 6 2 6 0.0000000000 0.0000000000
3 6 3 6 0.0062890119 0.0000000000
-------------------------------------------------------

--
D. R. Hamann Phone: 908-582-4454
Director, Theoretical Materials Fax: 908-582-4702
Physics Research (retired) email: drh@physics.bell-labs.com
Bell Laboratories Lucent Technologies
700 Mountain Ave, Room 1D-371
Murray Hill, NJ 07974-0636 USA

question abou the unit of rigid-atom elastic tensor in output file, Ha/(a.u.^3) or orther?, zfhou, 03/28/2005
- Re: [abinit-forum] question abou the unit of rigid-atom elastic tensor in output file, Ha/(a.u.^3) or orther?, D. R. Hamann, 03/28/2005