[Wien] Convergence problem
Muhammad Sajjad
sajjadpu at gmail.com
Sat Jan 3 07:02:33 CET 2015
Dear Tran and F. Gerhard
Many thanks for your help. With me the Cohesive Energies for NI and Fe are
5.53 eV/atom and 5.92eV/atom
On Thu, Jan 1, 2015 at 3:36 PM, <tran at theochem.tuwien.ac.at> wrote:
> From the total energies it's difficult to say. It's better to
> compare the cohesive energies. My cohesive energies for Fe and Ni
> with the WC functional are 5.54 and 5.38 eV/atom, respectively, with
> an error bar of 0.05 eV/atom maximum. In this paper you can find
> PBE cohesive energies calculated with the VASP code (my PBE values
> agree very well with them):
> http://journals.aps.org/prb/abstract/10.1103/PhysRevB.87.214102
>
> You have to know which error is acceptable for your purposes.
>
>
>
> On Thu, 1 Jan 2015, Muhammad Sajjad wrote:
>
> Dear Tran Thank you for your further help. I am also attaching here with
>> the structure file. Please let know the E0 values you calculated for Ni and
>> Fe. With me
>> these values are -3040.43215615 and -2544.39535597 (in Ry) respectively.
>>
>> On Tue, Dec 30, 2014 at 4:52 AM, <tran at theochem.tuwien.ac.at> wrote:
>> Hi,
>>
>> The struct file that I used is attached. For my purpose, the size of
>> the unit cell was large enough to avoid spurious interactions
>> between
>> neighbouring cells. Note that a, b and c are different in order to
>> avoid
>> to high symmetry.
>>
>> F. Tran
>>
>> On Mon, 29 Dec 2014, Muhammad Sajjad wrote:
>>
>> Dear Prof. Marks and F. TranThank you so much for your
>> helpful suggestions. I was already doing the spin polarization
>> calculations. I
>> have got the convergence
>> by using
>> mixing factor 0.1, starting calculation with PRATT and then
>> switched to MSR1 after 7 cycles, and the command runsp_lapw -cc 0.00001
>> -in1ef -i 150
>> The obtained magnetic moment was 2.00009.
>>
>> Dear Tran I would really appreciate if you share some more
>> details about case.struct file. It will definitely be helpful for me as well
>> as for others.
>>
>> Kind Regards
>> Dr. Sajjad
>>
>> On Mon, Dec 29, 2014 at 3:50 AM, <tran at theochem.tuwien.ac.at>
>> wrote:
>> The calculation for an isolated atom with a code which
>> uses periodic
>> boundary conditions (like WIEN2k) is not trivial. This
>> is what I have done
>> recently for most atoms of the periodic table
>> (excluding f-systems), and
>> for some of the transition-metal atoms this was
>> extremely difficult to
>> achieve convergence.
>>
>> A few hints (that I used):
>>
>> 1) It is important (and necessary depending on the
>> atom) to reduce the
>> symmetry from cubic to, e.g., orthorhombic to be able
>> to access the
>> electronic configuration with the lowest energy (this
>> is the procedure
>> followed by several research groups like VASP for
>> instance).
>> If necessary I can give more details about the
>> case.struct that I used.
>>
>> 2) lapw0 requires a lot of memory, while lapw1 requires
>> both
>> memory and time. To reduce computer time for lapw1, I
>> was using
>> iterative digonalization (this was my command for all
>> atoms):
>> runsp_lapw -ec 0.0001 -cc 0.0001 -it -i 1000 -NI
>>
>> 3) For the Ni atom the magnetic moment should be 2:
>> :MMTOT: SPIN MAGNETIC MOMENT IN CELL = 2.00238
>>
>> 4) I was using the default setting for mixer.
>>
>> F. Tran
>>
>> On Sun, 28 Dec 2014, Laurence Marks wrote:
>>
>>
>> Also, only 1 k-point (Gamma), an RMT and RKMax
>> similar to what you use for
>> bulk Ni, particularly as I assume you are doing
>> the calculation to get an
>> enthalpy of formation. You may have to use the
>> mpi versions as it is
>> probably too large for a non-mpi run.
>>
>> If you are doing WC+U (or -ineece) the U (or
>> on-site hybrid) removes the
>> phase transition so convergence should be simple.
>>
>> Straight WC is not a simple calculation because
>> the physics for an isolated
>> Ni atom is wrong. With wrong physics there is in
>> fact no guarantee that the
>> calculation will ever converge!
>>
>> ___________________________
>> Professor Laurence Marks
>> Department of Materials Science and Engineering
>> Northwestern University
>> www.numis.northwestern.edu
>> MURI4D.numis.northwestern.edu
>> Co-Editor, Acta Cryst A
>> "Research is to see what everybody else has seen,
>> and to think what nobody
>> else has thought"
>> Albert Szent-Gyorgi
>>
>> On Dec 28, 2014 11:47 AM, "Laurence Marks" <
>> L-marks at northwestern.edu> wrote:
>>
>> You almost certainly need to run spin
>> polarized, probably MSR1
>> (GREED 0.1), TEMPS (room temp). The
>> convergence is complicated
>> for WC (& simple GGAs) due to an electronic
>> phase transition
>> between sp & d occupation near the fixed
>> point.
>>
>> ___________________________
>> Professor Laurence Marks
>> Department of Materials Science and
>> Engineering
>> Northwestern University
>> www.numis.northwestern.edu
>> MURI4D.numis.northwestern.edu
>> Co-Editor, Acta Cryst A
>> "Research is to see what everybody else has
>> seen, and to think
>> what nobody else has thought"
>> Albert Szent-Gyorgi
>>
>> On Dec 28, 2014 10:47 AM, "Muhammad Sajjad"
>> <sajjadpu at gmail.com>
>> wrote:
>> Dear Users I am running SCF
>> calculation for Ni with
>> lattice constant of 30 Bohr and using
>> WC-GGA. The
>> calculation is not converging even
>> upto 100
>> iterations and more. To solve the
>> problem I have
>> performed following steps
>>
>> switched to TEMPS = 0.005 from TETRA
>> Changed MSR1 to PRATT
>> changed mixing factor (increase and decrease from
>> 0.2)
>>
>> Thanking in advance.
>>
>> Dr. Sajjad
>>
>>
>>
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>>
>>
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>>
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