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[David Waroquiers <david.waroquiers@uclouvain.be>]

Hello,

The stress target tensor you have defined is for a "negative" pressure, so the volume is increasing.
Indeed, the stress tensor can be separated into the hydrostatic term :
-P*I = (sigma11 + sigma22 + sigma33) / 3 * I (where P is the pressure and I is the unity matrix)
and a deviatoric term (which is equal to the sigma tensor minus the hydrostatic tensor).
So, for your case just add a minus sign in front of your terms in the strtarget variable and you will get what you want.

DWa

----- Original Message -----
From: vaskarpour@yahoo.com
Date: Sunday, September 13, 2009 2:51
Subject: [abinit-forum] high-pressure optimization of a triclinic cell
To: forum@abinit.org

> Dear abinit users,
> 
> I have optimized (at zero pressure) the triclinic cell in the 
> file below using
> GGA/PBE pseudopotentials.  However, when I apply a pressure 
> of 10GPa to the
> converged data, the lattice parameters and the volume keep 
> increasing with each
> Broyden step until the run stops with an error message asking me 
> to increase
> dilatmx (usually this is due to bad input lattice parameters, 
> but lowering the
> acell values does not help). This error occurs even if the 
> strtarget is only
> 1GPa. Can this error occur because strtarget is a symmetric 
> matrix but the
> rprim is not?
> I welcome any suggestions or hints.
> 
> Thanks,
> 
> Vahid
> 
> Vahid Askarpour
> Dalhousie University,
> Halifax, NS, Canada
> 
> optcell 2
> ionmov	2
> ntime	100
> dilatmx 1.2
> ecutsm	0.5
> kptopt 1          
> nshiftk 1
> shiftk	0.5 0.5 0.5  
> ngkpt	4 4 4
> nstep 100    
> toldff 5.0d-6
> diemac 12 
> acell  1.5982166823E+01  2.2574701588E+01  
> 1.5877524714E+01 
> angdeg	90.00  89.98  45.18
> strtarget 3.3989d-4 3.3989d-4 3.3989d-4 0 0 0
> strprecon 0.1
> strfact   100
> ntypat	2   
> znucl 1 53  
> natom 16          
> typat  1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2	
> xcart          
> 5.2789759836E+00  1.3873258360E+00  1.8122003932E+01
>               4.0777974016E-01 -1.8636312401E+00  1.8145708200E+01
>               1.9971806101E+00	6.2544357973E+00  1.8160224356E+01
>              -2.8465878874E+00	2.9868840816E+00  1.8165799855E+01
>               4.3516670737E+00	2.2014124412E+00  1.0197709596E+01
>               9.1952962180E+00	5.4690116409E+00  1.0189952760E+01
>               5.9408952033E+00	1.0319013175E+01  1.0212484138E+01
>               1.0699855971E+00	7.0691861142E+00  1.0233486481E+01
>              -2.7280551954E+00 -1.9351617833E+00  1.8154663922E+01
>               5.3556168486E+00 -1.7480977031E+00  1.8109183846E+01
>               5.1358591841E+00	6.3350137888E+00  1.8155935961E+01
>              -2.9277155210E+00	6.1257480651E+00  1.8169571282E+01
>               1.2129649071E+00	2.1227841094E+00  1.0202648261E+01
>               9.2753540349E+00	2.3303689459E+00  1.0185431498E+01
>               9.0765434282E+00	1.0392135358E+01  1.0204413627E+01
>               9.9156277398E-01	1.0204571422E+01  1.0245825277E+01
> ecut 15.0   
> iscf 7
> npulayit 15