The ABINIT Users Mailing List ( CLOSED )

[Masayoshi Mikami <mmikami@rc.m-kagaku.co.jp>]

Dear Zeming,

There are several points to be corrected/checked...

1)  Your input about the geometry is wrong.
At least, the followings to be added/corrected
spgroup 113 #  P-421m
natom 24 #  2*Ca2MgSi2O7 in the conventional cell
natrd 6

In passing, please check also "chkprim", "brvlatt" by consulting with
"Main ABINIT code, input variables:"
http://www.abinit.org/Infos_v4.4/keyhr.html
...this is a sort of homework. ;-)

Read also FAQ, for example,
http://www.abinit.org/about/?text=../Infos/FAQ#setup
http://www.abinit.org/about/?text=../Infos/FAQ#crystal_data

2) Before cell optimization (optcell > 0), geometry optimization
(ionmov 2 or 3) with optcell 0 should come first... in general.
If not, one may have collapsed unit cells...

3) There is a nice ABINIT work on Akermanite :
 Razvan Caracas and Xavier Gonze, Phys. Rev. B 68, 184102 (2003)
 http://link.aps.org/abstract/PRB/v68/e184102
You might want to refer to the paper.

In any case, please try attached Test_*/Tutorials
before running your own calculations. Then you will find not a few
of the input files useful as templates for your own jobs.

Good luck,
Masayoshi

On 2005/03/15, at 1:25, zmq.lyao@gmail.com wrote:

> Dear Abinit users,
>    I try to perform a lattice optimization calculation of Ca2MgSi2O7. 
> But It can't converge after 30 Broyd/MD steps. My input is as follows. 
> Becauae I am a new user of abinit and not familiar with these input 
> variables, I would appreciate that anyone can give me some 
> suggestions.
> The Pseudopotential I used: Troullier-Martins pseudopotentials for Si 
> and O,Hartwigsen-Goedecker-Hutter psp for Ca and Mg.
> The abinit version is 4.4.3 for a P6/DOS/Windows computer.
> ---------------------------------------
> # Crystalline Ca2MgSi2O7 : computation of the total energy
> #
> #Optimization of the lattice parameters
> optcell 1
> ionmov  2
> ntime  30
> dilatmx 1.05
> ecutsm  0.5
> toldff = 5.0D-5
> tolmxf = 1.0D-4
>
> #Definition of the unit cell
> acell 14.79206 14.79206 9.46125          # This is lattice constant
> rprim  1.0  0.0  0.0
>     0.0  1.0  0.0
>     0.0  0.0  1.0
>
> #Definition of the atom types
> ntypat 4
> znucl 20 12 14 8
>
> #Definition of the atoms
> natom 6           # There are six atoms
> typat 1 2 3 4 4 4
> xred
> 0.3320 0.1680 0.5050
> 0      0      0
> 0.1395 0.3605 0.9334
> 0.5 0.0 0.1775
> 0.1409 0.3591 0.2547
> 0.0816 0.1870 0.7879
>
> ecut 85
>
> #Definition of the k-point grid
> kptopt 1          # Option for the automatic generation of k points, 
> taking
>                # into account the symmetry
>
> ngkpt 2 2 2
> nshiftk 1
> shiftk 0.5 0.5 0.5
>
> #Definition of the SCF procedure
> nstep 60          # Maximal number of SCF cycles
>
> diemac 12.0
> ------------------------------
>
> Regards,
> Zeming