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["#TAO JUNGUANG#" <TAOJ0003@ntu.edu.sg>]

Thanks for the comments. 

The input file is given below. I do forget using ecutsm. Because I am doing it manually, meaning I change the lattice constant manually, and looking for the one who give us lowest energy. I do not rely on optcell and ionmov. In this case, still the ecutsm necessary? The reason I do it manually is because I found by using optcell and ionmov give me different results. I don’t know the mechanism behind for optcell and ionmov, I m kind of more prefer manually tune the value. ( because you are kind of control it)

Now, I change the ecut to 30 hartree, the results look much better. But the optimized lattice constants changed a lot, around 0.04 angstrom. 

 

Any comment on these? 1, how important role the ecutsm play if I do it by manually tuning the value? 2, do ecutsm really help without increasing the ecut? Because when increase the ecut, the cpu time increase several times. If ecutsm is really reliable for doing the job. I prefer use it instead. I don’t much experience with this, hope you can give some comment. Thank you.

 

 

======================================================

 

# Crystalline TiO2

 

#Optimization of the lattice parameters

 

ecut 10.0

 

#acell 2*4.59373 2.95812 angstrom

 

acell 2*4.55 2.93   angstrom

 

 

kptopt 1

ngkpt 4 4 6

toldfe 1.0d-10

nband 48

ntypat 2 

znucl 22 8 

 

natom 6 

typat 1 1 2 2 2 2 

xred 

  0.00000000  0.00000000   0.00000000      #Ti

  0.50000000  0.50000000   0.50000000      #Ti

  0.30200746218   0.30200746218   0.000

  -0.30200746218  -0.30200746218  0.000

  0.80200746218   0.19799253782   0.5000

  0.19799253782   0.80200746218   0.500

 

nstep 30

diemac 2.0

 

---

From: Xavier Gonze [mailto:gonze@pcpm.ucl.ac.be]
Sent: 2007年5月2日 12:28 PM
To: forum@abinit.org
Subject: [abinit-forum] Lattice optimization

 

Dear Tao Junguang,

 

You should have sent your input file, for us to comment correctly on that result.

 

Well, in the absence of that file ...

This effect might be due to the fact that you did not define ecutsm (well, you might

as well increase ecut to death and obtain something smooth, but a small ecutsm 

will do the work).

If you indeed forgot to define ecutsm, you should follow lesson 3 of the tutorial, where the way to obtain

the lattice parameter is explained in detail. 

 

Best,

Xavier

 

On 30 Apr 2007, at 14:45, #TAO JUNGUANG# wrote:

When I optimize my rutile tio2 structure use the procedure I mentioned previously. The result looks very strange.

 

The figure below is the Etotal/Hartree vs the a/Angstrom, while keep c/a fixed as experimental value. The total energy minimized at reasonable value. But, is the curve supposed to be smooth, because I got a smooth one when using other software like pwscf.

 

 I think maybe it’s the pseudopotential, because at beginning, when I use other ones, I can not even get something like this.  The pseudopotential I used is o-ps.abinit.paw.lda.nocore and ti-ps.abinit.paw.lda( sorry the files is too large to attach), can any one give some comments?

 

 

 

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