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[Lallet François <francois.lallet@umontreal.ca>]

Dear Zhang,

No I didn't try to calculate the elastic constant/tensor... The paper C S G 
Cousins 1981 J. Phys. C: Solid State Phys. 14 1585-1602   
doi:10.1088/0022-3719/14/11/019 deals with strain tensors in corundum... I 
didn't check it in details but maybe you can find usefull references related 
to elastic/stress/strain tensors therein... 
Best,

F. Lallet 


-----Original Message-----
From: waigen zhang [mailto:waigen.zhang@gmail.com]
Sent: Mon 6/11/2007 1:15 PM
To: forum@abinit.org
Subject: Re: [abinit-forum] structural geometry of alfa-Al2O3
 
Dear Lallet,
Thank you for your replies.
Have you tried to calculate the elastic constant? There are several ways to
define the structural geometry for alpha-Al2O3 and it seems the nonzero
elements in the elastic tensor are different if we choose different
geometry.

W.G.Zhang


On 6/9/07, Lallet François <francois.lallet@umontreal.ca> wrote:
>
> Dear Zhang,
> I followed the instruction on webpage
> http://cst-www.nrl.navy.mil/lattice/struk/d5_1.html. and I studied the
> relaxation of the alpha Al2O3 rhombohedral unit cell with ionmov=2;
> optcell=2, ngkpt=2 2 2 and ecut was fixed to 15Ha (I used PAW
> pseudopotentials produced with atompaw) in LDA and GGA. The energy was
> converged within 0.2eV/atom and the forces relaxed below 10^-4Ha/(
> Bohr.atom), which was sufficient to produce relaxed lattice parameters and
> internal ionic positions (see Wyckoff "Crystal Structure" is you have any
> doubts) in very good agreement with experiments. I calculated also the bulk
> modulus by fitting E(V) with a Murnaghan equation of state and the results
> are very good... but I don't know whether the hexagonal unit cell is better
> than the rhombohedral one for this purpose...
> Best,
>
> F. Lallet
>
> -----Original Message-----
> From: waigen zhang [mailto:waigen.zhang@gmail.com]
> Sent: Fri 6/8/2007 3:52 PM
> To: forum@abinit.org
> Subject: [abinit-forum] structural geometry of alfa-Al2O3
>
> Dear all,
> Dose anybody have idea about the structural geometry about alfa-Al2O3 ?
> Should we use the rhombohedral or hexagonal primitive cell for ABINIT
> calculation of elastic constant?
> I followed the instruction on webpage
> http://cst-www.nrl.navy.mil/lattice/struk/d5_1.html.
> But still not sure about that. Your suggestion is welcome.
>
> Best,
> W.G.Zhang
>
>
>

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