The value of the fermi energy is not a "proper" quantity in a
calculation of an infinite solid. It depends on the zero of energy, and
this is set to the mean interstitial potential. These changes are
unusual, but a priory no reason to worry.
You can see this shift of the energy-zero by looking at some core
eigenvalues:
grepline ':1s 001' '*scf' 1 will show you the same variations as EF.
PS: Linear dependency would either lead to a crash or at least a
significant change of total energy.
PPS: It is very valuable that you test for convergence. But you must
test these quantities which you want to publish. EF is not the right one.
------------------------
However, I would worry about the accuracy of your calculations in
general. You are using RMT values of 2.8 bohr (much larger than the
setrmt limit of 2.5 - which is already a compromise).
Large spheres are of course possible, but then you have to make sure
that all expansions are converged:
grep :FIT case.scf shows a value of 0.1E-01, indicating that the
nonspherical potential at large R is very large.
This requires a couple of changes in the default inputs:
LNSmax in case.in1 must be increased from 4 to 6 or even 8 (most severe
!! changes E-tot by several mRy)
The LM list (case.in2) should be enlarged. Adding the L=8 terms (see UG)
reduces :FIT by an order of magnitude.
Y-d states may have a linearization error. Add a HDLO for them.
Also: When varying RKMAX in such a large range, GMAX (in2) and the
IFFT-parameters (in0) may also have to be increased.
On 07/26/2017 06:47 PM, Arena Konta wrote:
Dear Wien2k Users,
How to check if my calculations are beyond "approximate numerical linear
dependency"? The below calculations were converged with the criterion -ec 0.000001 and
-cc 0.000001 on a fine mesh k-point to determine a good Fermi level energy accuracy (simple
mettalic 3D compound cointaining Y and Al elements). No warning in scf file is appeared.
From RKmax>=10 onwards the change in energy differences is smaller than 0.0002 Ry,
hovewer I have problems with convergation the value of the Fermi Energy. What should I do to
obtain better accuracy of EF?
limit due to "approximate numerical linear dependency"
7
:ENE : ********** TOTAL ENERGY IN Ry = -49933.78396516
:DIS : CHARGE DISTANCE ( 0.000000 for atom 2 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4453031967
7.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.79802481
:DIS : CHARGE DISTANCE ( 0.000000 for atom 2 spin 1) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4533274885
8.0
:ENE : ********** TOTAL ENERGY IN Ry = -49933.80529502
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4605712711
:DIS : CHARGE DISTANCE ( 0.000000 for atom 2 spin 2) 0.000001
8.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.80900587
:DIS : CHARGE DISTANCE ( 0.000000 for atom 2 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4674101982
9.0
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81083697
:DIS : CHARGE DISTANCE ( 0.000000 for atom 2 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4741770929
9.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81174098
:DIS : CHARGE DISTANCE ( 0.000000 for atom 2 spin 2) 0.000002
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4805577469
10
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81217067
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 1) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4863678502
10.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81237951
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 1) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4918538304
11
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81247632
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.4970660550
11.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81252520
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5020619935
12
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81255122
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 1) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5069889516
12.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81257047
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 1) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5113533412
13.00
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81257716
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5141763509
13.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81258348
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5142562275
14
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81258360
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5122039226
14.5
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81258849
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5094474844
15
:ENE : ********** TOTAL ENERGY IN Ry = -49933.81258989
:DIS : CHARGE DISTANCE ( 0.000000 for atom 1 spin 2) 0.000001
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.5065405179
Thank you
Arena
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P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
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