Dear Eduardo, Andrei and all:
Here is another question following the previous one.
I try to calculate the cohesive energy for certain carbon solid
system, for example, diamond. It is no problem to get a converged
total energy for diamond with respect to energy shift. However, we
have problem to get a proper reference energy for a single carbon
atom which does not converge with respect to energy shift. What do
you think if I just choose the same energy shift for carbon atom
as the one used in diamond solid system calculation? Does it help
to cancel some calculation error if we use same energy shift for
both systems?
Thank you very much!
Sincerely yours,
Xu Lu
======================================
Xu Lu
---------------
Physics and Astronomy Department
4240 Biomedical &Physical Sci. Bldg
Michigan State University
East Lansing, MI 48824-2320 USA
(517)884-5672 (office)
(517)4205973 (mobile)
(517)353-4500 (FAX)
http://www.msu.edu/~luxu
======================================
Eduardo Anglada writes:
Hi,
When you increase the energy shift then you decrease the cutoff radii,
so the energy increases. The behaviour of your plot is exactly what
you should expect. What you should converge is the total energy of
your condensed system, formed by multiple atoms. In that situation
the energy should converge (with a tolerance of a few mev) with
respect to the energy shift.
Best regards,
Eduardo
On 03/11/2008, at 19:13, Xu Lu wrote:
Dear Eduardo and all:
Thank you very much for your reply. Here I give you one of
my input files and other information:
===================== start of input file=========================
SystemName carbon atom # Descriptive name of the system
SystemLabel C-atom # Short name for naming files
# Species and atoms
NumberOfSpecies 1
NumberOfAtoms 1
%block ChemicalSpeciesLabel
1 6 C
%endblock ChemicalSpeciesLabel
# Basis (TZP)
%block PAO.Basis # Define Basis set
C 2 # Species label, number of l-shells
n=2 0 3 # n, l, Nzeta
0.000 0.000 0.000
1.000 1.000 1.000
n=2 1 3 P 1 # n, l, Nzeta, Polarization, NzetaPol
0.000 0.000 0.000
1.000 1.000 1.000
%endblock PAO.Basis
PAO.EnergyShift 10 meV
xc.functional LDA # Default value
xc.authors PZ # Default value
MeshCutoff 300. Ry
OccupationFunction MP
ElectronicTemperature 100 K
# SCF options
MaxSCFIterations 150 # Maximum number of SCF iter
DM.NumberPulay 5
DM.MixingWeight 0.20 # New DM amount for next SCF cycle
DM.Tolerance 1.d-4 # Tolerance in maximum difference
# between input and output DM
# Atomic coordinates
AtomicCoordinatesFormat Ang
%block AtomicCoordinatesAndAtomicSpecies
0.000000000000 0.000000000000 0.000000000000 1
%endblock AtomicCoordinatesAndAtomicSpecies
======================= end of input file=========================
You can also have a look at a plot of my total energy convergence
results with respect to energy shift.
https://www.msu.edu/~luxu/singlecarbon-data.png
It seems hard to achieve Self-Consistency at zero electronic
temperature, I used electron temperature at 100.0 K and MP
(Methfessel-Paxton)occupation function and I hope this set up
is not the reason of problems.
Thank you again for your kind helps!
Sincerely yours,
Xu Lu
======================================
Xu Lu
---------------
Physics and Astronomy Department
4240 Biomedical &Physical Sci. Bldg
Michigan State University
East Lansing, MI 48824-2320 USA
(517)884-5672 (office)
(517)4205973 (mobile)
(517)353-4500 (FAX)
http://www.msu.edu/~luxu
======================================
Eduardo Anglada writes:
Hi,
Could you please post your results and the input fdf?
The energy should converge.
Best
Eduardo On 01/11/2008, at 15:23, Xu Lu wrote:
Dear all :
I have a problem in calculating the energy of single atom. The
energy will drop linearly with respect to decreasing of energy shift.
It
seems that the energy does not converge with respect to energy shift.
What is the problem with single atom calculation ? Do I need to
consider the energy shift convergence in this calculation.
