[Wien] Convergence problem
Muhammad Sajjad
sajjadpu at gmail.com
Thu Jan 1 15:06:48 CET 2015
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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