Convergence with respect to TSMEAR

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Boris
Posts: 128
Joined: Tue Feb 16, 2010 10:13 am
Location: France

Convergence with respect to TSMEAR

Post by Boris » Tue Mar 22, 2011 5:04 pm

Hi all,

The keyword tsmear isn't usually something for which I'm doing convergence tests... I know, it's bad. I'm now dealing with a metal, so I decided to run a convergence test with respect to tsmear. And I got something very strange, compared to what a convergence test should give. Below is the result, it represents the difference in energy (in meV/atom) between a dataset (N) and the previous one (N-1), so it should tend towards 0. The tsmear value starts at 0.002 Ha and ends at 0.160 Ha

Image

This is strange, isn't it? It is kind of difficult to choose a value for tsmear with such a plot... Abinit suggests 0.01 Ha for d-band metals. At 0.01 Ha, the convergence curve just starts to increase. I'm quite puzzled about this. Could someone share its experience about this?

Thank you very much

Boris

PS: I got occopt=6 and a 11x11x9 kpoint mesh (80 kpts in the BZ).
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Boris Dorado
Atomic Energy Commission
France
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sittichain
Posts: 4
Joined: Mon May 23, 2011 9:00 am

Re: Convergence with respect to TSMEAR

Post by sittichain » Wed Jun 29, 2011 9:58 am

Hi Boris!
i have the same problem, i am trying to make the convergence test of C60 with respect to tsmear using occopt 3 and 7. In both occopt 3 and 7 cases, the results show the systems have lower energy with higher tsmear. But with high tsmear, the density of states exhibit that C60 have metallic properties, DOS is continuous in the vicinity of the Fermi level. It is absolutely sure C60 isn't metal and this results is strange. It is probably to set inappropriate tsmear can break the variational principle. Or i assign other input variables wrong. Now if someone can make it clear, please share me your experience. I will be appreciated your help.

my in put file for occopt=3
occopt 3
ndtset 11
tsmear: 0.001 tsmear+ 0.005

#Definition of the unit cell
acell 20 20 20
rprim 1 0 0
0 1 0
0 0 1
#Definition of the atom types
ntypat 1
znucl 6

#Definition of the atoms
natom 60
typat 60*1
xcart 8.8643 6.5466 12.8101
7.2628 8.7508 12.8101
4.6716 7.9089 12.8101
4.6716 5.1843 12.8101
7.2628 4.3424 12.8101
12.9875 7.9089 7.6706
11.8286 8.7508 9.9884
11.1124 6.5466 11.4208
11.8286 4.3424 9.9884
12.9875 5.1843 7.6706
7.2413 13.0932 7.6706
6.0825 12.2513 9.9884
7.9575 10.8890 11.4208
1.0275e+01 1.0889e+01 9.9884e+00
9.8326e+00 1.2251e+01 7.6706e+00
5.3500e-01 9.2304e+00 7.6706e+00
9.7777e-01 7.8681e+00 9.9884e+00
2.8528e+00 9.2304e+00 1.1421e+01
3.5690e+00 1.1435e+01 9.9884e+00
2.1365e+00 1.1435e+01 7.6706e+00
2.1365e+00 1.6586e+00 7.6706e+00
3.5690e+00 1.6586e+00 9.9884e+00
2.8528e+00 3.8628e+00 1.1421e+01
9.7777e-01 5.2251e+00 9.9884e+00
5.3500e-01 3.8628e+00 7.6706e+00
9.8326e+00 8.4189e-01 7.6706e+00
1.0275e+01 2.2042e+00 9.9884e+00
7.9575e+00 2.2042e+00 1.1421e+01
6.0825e+00 8.4189e-01 9.9884e+00
7.2413e+00 2.1758e-05 7.6706e+00
8.4216e+00 7.9089e+00 2.8310e-01
5.8304e+00 8.7508e+00 2.8310e-01
4.2289e+00 6.5466e+00 2.8310e-01
5.8304e+00 4.3424e+00 2.8310e-01
8.4216e+00 5.1843e+00 2.8310e-01
1.0957e+01 1.1435e+01 5.4226e+00
9.5242e+00 1.1435e+01 3.1048e+00
1.0240e+01 9.2304e+00 1.6724e+00
1.2115e+01 7.8681e+00 3.1048e+00
1.2558e+01 9.2304e+00 5.4226e+00
3.2606e+00 1.2251e+01 5.4226e+00
2.8180e+00 1.0889e+01 3.1048e+00
5.1357e+00 1.0889e+01 1.6724e+00
7.0107e+00 1.2251e+01 3.1048e+00
5.8519e+00 1.3093e+01 5.4226e+00
1.0566e-01 5.1843e+00 5.4226e+00
1.2646e+00 4.3424e+00 3.1048e+00
1.9808e+00 6.5466e+00 1.6724e+00
1.2646e+00 8.7508e+00 3.1048e+00
1.0566e-01 7.9089e+00 5.4226e+00
5.8519e+00 2.1758e-05 5.4226e+00
7.0107e+00 8.4189e-01 3.1048e+00
5.1357e+00 2.2042e+00 1.6724e+00
2.8180e+00 2.2042e+00 3.1048e+00
3.2606e+00 8.4189e-01 5.4226e+00
1.2558e+01 3.8628e+00 5.4226e+00
1.2115e+01 5.2251e+00 3.1048e+00
1.0240e+01 3.8628e+00 1.6724e+00
9.5242e+00 1.6586e+00 3.1048e+00
1.0957e+01 1.6586e+00 5.4226e+00

#Definition of the planewave basis set
ecut 10.0 # Maximal plane-wave kinetic energy cut-off, in Hartree
prtdos 1
prtden 1

#Definition of the k-point grid
kptopt 0 # Enter the k points manually
nkpt 1 # Only one k point is needed for isolated system,
# taken by default to be 0.0 0.0 0.0

#Definition of the SCF procedure
nstep 10 # Maximal number of SCF cycles
toldfe 1.0d-6
diemac 2.0


thank you
Sittichain

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