I have obtained the equilibrium lattice constant, bulk modulus of the bulk platinum (Pt) using fitting the BM-EOS, which agree well with experiments and other PW methods, but how to accurately get hte cohesive energy (Ecoh)using Exciting code? I know that this code can solve the problem of non-periodic boundary like molecules, clusters. Comparing with the Ecoh (Etot(bulk Pt) - Etot(isolated Pt atom) (about 5.8 eV) from the PW methods or experiments, however, my calculated result using Exciting is too smaller, only 1.5 eV!!! Please experenced user tell me how to reduce this gap. Here I attach my input files for Pt bulk and single Pt atom.
Thanks in advance!
Regards,
Hu
========Pt_bulk================
! Try and find the equilibrium volume of fcc Pt
For the largest scale, I get E_solid-E_atom=5.768 eV, which is quite close to experiment.
Incidently, using molecule=.true. simply sets up a simple cubic unit cell with sides of length "vacuum". I wonder if you could do me a favour and find which is the best unit cell (and vacuum length) for computing atoms and molecules (is it fcc, bcc or simple cubic?). If something other than simple cubic is best then I can change the "molecule" mode for the next release.
Could anyone please suggest what could be the problem of strong
total energy oscillations while calculating the ground state
of the 16-atomic hexagonal Mn5Ge3 crystal?
I tried to increase input parameters like rgkmax, k-points mesh,
nempty, but the problem still exists and I cannot receive
the total energy convergence.
Here is my input file.
Any ideas will be greatly appreciated!
Regards,
Yvett
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
! Ferromagnetic Mn5Ge3. Note the small global magnetic field, which
! is needed to break spin symmetry. Check the total moment of the cell in the
! file INFO.OUT.
tasks
0
spinpol
.true.
! small magnetic field (NOT in the z-direction)
bfieldc
0.0 0.0 0.01
! fairly large number of empty states required for magnetic cases
nempty
10
avec
13.575797890 0.000000000 0.000000000
-6.787898945 11.756985849 0.000000000
0.000000000 0.000000000 9.548789913
Hi!
The first thing I would try is to decrease the mixing parameter from default to 0.05:
beta0
0.05
The second thing I would try is to increase the number of kpoints, and remove the shift also.
ngridk
4 4 6
For example 4 4 6 seems reasonable to me, since you have c/a about 0.7 the number of kpoints along z directions should be around (0.7)^(-1) = 1.3 the number of kpoints along the other two directions.
If still does not converge , you may also try 6 6 8.
By the way remeber to converge all parameters before to perform a "productive" calculation.
If you are interested in tiny energy differences such as meV for different magnetic structures you may also increase lmaxapw,lmaxmat,lmaxvr.
Hope this will help!
Best
Francesco Cricchio
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Dear exciting users,
I have obtained the equilibrium lattice constant, bulk modulus of the bulk platinum (Pt) using fitting the BM-EOS, which agree well with experiments and other PW methods, but how to accurately get hte cohesive energy (Ecoh)using Exciting code? I know that this code can solve the problem of non-periodic boundary like molecules, clusters. Comparing with the Ecoh (Etot(bulk Pt) - Etot(isolated Pt atom) (about 5.8 eV) from the PW methods or experiments, however, my calculated result using Exciting is too smaller, only 1.5 eV!!! Please experenced user tell me how to reduce this gap. Here I attach my input files for Pt bulk and single Pt atom.
Thanks in advance!
Regards,
Hu
========Pt_bulk================
! Try and find the equilibrium volume of fcc Pt
tasks
0
avec
0.5 0.5 0.0
0.5 0.0 0.5
0.0 0.5 0.5
scale1
7.52000
scale2
7.52000
scale3
7.52000
scale
1.00
! large cut-off is required for Cu
rgkmax
8.5
lmaxapw
10
gmaxvr
14.0
sppath
'../../species/'
atoms
1 : nspecies
'Pt.in' : spfname
1 : natoms
0.0 0.0 0.0 0.0 0.0 0.0 : atposl, bfcmt
ngridk
10 10 10
xctype
20
=======Pt atom===================
! Pt-atom.
tasks
0
! molecule calculation
molecule
.true.
! finding symmetries for large systems can be prohibitive
nosym
.true.
rgkmax
8.5
lmaxapw
10
gmaxvr
14.0
spinpol
.true.
taufsm
0.01
fixspin
.true.
momfix
0.0 0.0 2.0
sppath
'../../species/'
atoms
1 : nspecies
'Pt.in' : spfname
1 : natoms; atpos, bfcmt below
0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000
xctype
20
Dear Hu,
Sorry for the delay in replying.
I think the problem may be that your vacuum layer may be too small (the default is vacuum=8.05 a.u.).
I've tried various unit cell sizes (not using molecule=.true., just a large fcc box, exciting.in is below) and obtain
scale E_solid-E_atom
20.0 0.21198
18.0 0.20660
16.0 0.19960
14.0 0.17609
12.0 0.11769
10.0 0.04155
For the largest scale, I get E_solid-E_atom=5.768 eV, which is quite close to experiment.
Incidently, using molecule=.true. simply sets up a simple cubic unit cell with sides of length "vacuum". I wonder if you could do me a favour and find which is the best unit cell (and vacuum length) for computing atoms and molecules (is it fcc, bcc or simple cubic?). If something other than simple cubic is best then I can change the "molecule" mode for the next release.
Cheers,
Kay.
---------------------------- solid ----------------------------
tasks
0
avec
0.5 0.5 0.0
0.5 0.0 0.5
0.0 0.5 0.5
scale1
7.52000
scale2
7.52000
scale3
7.52000
scale
1.00
! large cut-off is required for Cu
rgkmax
8.0
lmaxapw
10
gmaxvr
14.0
atoms
1 : nspecies
'Pt.in' : spfname
1 : natoms
0.0 0.0 0.0 0.0 0.0 0.0 : atposl, bfcmt
ngridk
10 10 10
xctype
20
------------------------------------------------------------------
---------------------------- molecule ----------------------------
tasks
0
beta0
0.01
avec
0.5 0.5 0.0
0.5 0.0 0.5
0.0 0.5 0.5
scale
20.0
! large cut-off is required for Cu
rgkmax
8.0
lmaxapw
10
gmaxvr
14.0
atoms
1 : nspecies
'Pt.in' : spfname
1 : natoms
0.0 0.0 0.0 0.0 0.0 0.0 : atposl, bfcmt
ngridk
1 1 1
xctype
20
------------------------------------------------------------------
Dear EXCITING users,
Could anyone please suggest what could be the problem of strong
total energy oscillations while calculating the ground state
of the 16-atomic hexagonal Mn5Ge3 crystal?
I tried to increase input parameters like rgkmax, k-points mesh,
nempty, but the problem still exists and I cannot receive
the total energy convergence.
Here is my input file.
Any ideas will be greatly appreciated!
Regards,
Yvett
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
! Ferromagnetic Mn5Ge3. Note the small global magnetic field, which
! is needed to break spin symmetry. Check the total moment of the cell in the
! file INFO.OUT.
tasks
0
spinpol
.true.
! small magnetic field (NOT in the z-direction)
bfieldc
0.0 0.0 0.01
! fairly large number of empty states required for magnetic cases
nempty
10
avec
13.575797890 0.000000000 0.000000000
-6.787898945 11.756985849 0.000000000
0.000000000 0.000000000 9.548789913
!scale
!1.00
sppath
'../../species/'
atoms
2 : nspecies
'Mn.in' : spfname
10 : natoms
0.33333333 0.66666667 0.00000000 0.0 0.0 0.1 : atposl, bfcmt
-0.33333333 -0.66666667 0.00000000 0.0 0.0 0.1
0.66666667 0.33333333 0.50000000 0.0 0.0 0.1
-0.66666667 -0.33333333 -0.50000000 0.0 0.0 0.1
0.23900000 0.00000000 0.25000000 0.0 0.0 0.1
-0.23900000 0.00000000 -0.25000000 0.0 0.0 0.1
0.00000000 0.23900000 0.25000000 0.0 0.0 0.1
0.00000000 -0.23900000 -0.25000000 0.0 0.0 0.1
-0.23900000 -0.23900000 0.25000000 0.0 0.0 0.1
0.23900000 0.23900000 -0.25000000 0.0 0.0 0.1
'Ge.in' : spfname
6 : natoms
0.60300000 0.00000000 0.25000000 0.0 0.0 0.1
-0.60300000 0.00000000 -0.25000000 0.0 0.0 0.1
0.00000000 0.60300000 0.25000000 0.0 0.0 0.1
0.00000000 -0.60300000 -0.25000000 0.0 0.0 0.1
-0.60300000 -0.60300000 0.25000000 0.0 0.0 0.1
0.60300000 0.60300000 -0.25000000 0.0 0.0 0.1
autormt
.true.
rgkmax
6.0
ngridk
2 2 4
vkloff
0.5 0.5 0.5
Hi!
The first thing I would try is to decrease the mixing parameter from default to 0.05:
beta0
0.05
The second thing I would try is to increase the number of kpoints, and remove the shift also.
ngridk
4 4 6
For example 4 4 6 seems reasonable to me, since you have c/a about 0.7 the number of kpoints along z directions should be around (0.7)^(-1) = 1.3 the number of kpoints along the other two directions.
If still does not converge , you may also try 6 6 8.
By the way remeber to converge all parameters before to perform a "productive" calculation.
If you are interested in tiny energy differences such as meV for different magnetic structures you may also increase lmaxapw,lmaxmat,lmaxvr.
Hope this will help!
Best
Francesco Cricchio