ABINIT Discussion Forums

Hello Dear users!
I study the effect of high pressure on Ti13 cluster.
Can you help me to understand how to optimization of Ti13 cluster structure under high pressure?
My input file:
acell 30 30 30
##### Pressure -0.5 GPa
strtarget 1.69946446135d-5 1.69946446135d-5 1.69946446135d-5 0 0 0
strprecon 0.1
strfact 100
##########################
prtgeo 2
enunit 1
ionmov 2
tolmxf 1.0d-4
diemac 1.6d0
diemix 0.5d0
ecut 30
ecutsm 0.5
natom 13
# iprcel 45
nline 20
# nnsclo
# nband 11
##########################
kptopt 1
nshiftk 1
shiftk 0.0 0.0 0.0
ngkpt 1 1 1
##########################
nsppol 2
occopt 1
# tsmear 1.0d-3
nstep 500
ntime 500
nsym 1
ntypat 1
rprim 1 0 0
0 1 0
0 0 1

toldfe 1.d-6
typat 1 1 1 1 1 1 1 1 1 1 1 1 1
xangst 6.8090113573E-02 2.2648002162E+00 3.6989886424E+00
2.3289618852E+00 3.6563155534E+00 4.2295202449E-02
2.3336571107E+00 3.6517277472E+00 4.6372808991E+00
4.5857679946E+00 2.3858801434E+00 9.4579361802E-01
9.4418155531E-01 1.0680097784E-01 2.3700037108E+00
9.2574436618E-01 4.5577919790E+00 2.3108132390E+00
2.3254215603E+00 9.8871116578E-01 4.6087972220E+00
3.7913661176E+00 4.5491234222E+00 2.2788477266E+00
2.3626986158E+00 9.7371995677E-01 8.9448900154E-02
4.5534668769E+00 2.3854016394E+00 3.7289287822E+00
3.6160073483E+00 3.0380260838E-02 2.2533604234E+00
9.1551423389E-02 2.3344500838E+00 9.4551882884E-01
2.3179313366E+00 2.3597431585E+00 2.3347691094E+00

znucl 22
# This line added when defaults were changed (v5.3) to keep the previous, old behaviour
iscf 7

Best regards,
Andrey Chibisov.
Numerical method of mathematical physics Laboratory
Computing Center of Far Eastern Branch of Russian Academy of Sciences

Hi,
If I understand your input file correctly (and I may not), I'm not sure you can get an interesting answer this way. It appears that you have set up a large, empty box and placed a Ti13 cluster at each corner, right? That's the correct way to study an isolated molecule with a code like abinit. But then you want to apply pressure--but there's no medium in the system to transmit the pressure to the clusters, because the box is empty, except for the clusters. So I don't think you can get anything out of this approach. If you were doing it experimentally, I think you would have a gas in the container (like neon or argon) as the pressurizing fluid, and then the Ti13 clusters would be pressurized by the force of the Ne or Ar on them. You could simulate that situation in abinit, but it will be a very complex calculation.

Two other alternatives,which are different from the above and not all that close to the experimental situation, would be: 1) simply decrease acell until the clusters start interacting with each other--now you have a primitive cubic "solid Ti13" phase that is pressurizing itself. Or, leave acell as it is but artificially contract all the Ti-Ti bonds and see what happens for example to the DOS. This is not the same as external pressure but it may get at what you are trying to learn anyway.

best wishes,