Dear Max,
I think that this rule is a myth, for the simple reason that more
ecutwfc=more plane waves = more energy, In addition to that , the more
system is big the bigger is the energy (and the energy jumps vs
ecutwfc).
I suggest you to rerun the calculations with tstress = .true. &
tprnfor = .true. , then you look after on the impact of ecutwfc upon
force and stress tensor.
By plotting your data, I suggest that ecutwfc threshold is laying
between 50 to 150 Ry.
On Fri, Jul 10, 2015 at 1:02 AM, max <[email protected]> wrote:
Dear Youssef and Giovanni,
Thank you very much, I have doubt about convergence energy.
I run scf calculations for ecutwfc from 10 to 250 Ry using
ecutrho=4*ecutwfc and I get the values bellow ecutwfc vs etotal
(values in Ry). I read that the convergence will be achieved when the
difference between two adjacent scf calculation is smaller than 0.1
meV [1] or 1 mRy [2], but this is for unit cell or for atoms (divide
the energy difference between the number of atoms in unit cell)?
Other question, is normal that the convergence value for ecutwfc be
more than 200 Ry?
ecutwfc etotal
10 -941.67085713
15 -1005.07732548
20 -1038.00240543
25 -1058.8736733
30 -1073.25016374
35 -1082.62081233
40 -1089.10688841
45 -1093.8583202
50 -1097.63582121
55 -1100.63775846
60 -1103.0243432
65 -1105.15423136
70 -1107.08545327
75 -1108.79020201
80 -1110.27166937
85 -1111.59023819
90 -1112.768963
100 -1114.66472444
110 -1116.05760199
120 -1117.06611139
130 -1117.76952606
140 -1118.25442342
150 -1118.58413784
160 -1118.80480982
170 -1118.95194442
180 -1119.0489105
190 -1119.11208313
200 -1119.15329918
210 -1119.17990393
220 -1119.19703143
230 -1119.20790385
240 -1119.21481705
250 -1119.21915626
[1] https://www.mail-archive.com/pw_forum%40pwscf.org/msg11093.html
[2] http://qe-forge.org/pipermail/pw_forum/2013-February/101122.html
On Tue, Jul 7, 2015 at 7:35 PM, Youssef <[email protected]> wrote:
Dear Max,
You can use the following 14 atoms coordinates for spinel AB2O4
(fd-3m origin choice 2), replace "x" with oxygen parameter from 32e
wykoff site (0.2627 for your case)
A 0.125 0.125 0.125
A 0.875 0.375 0.375
B 0.5 0.5 0.5
B 0.25 0.75 0
B 0.75 0 0.25
B 0 0.25 0.75
O (x) (x) (x)
O (1.25-x) (x+0.5) (1.75-x)
O (x+0.75) (x+0.25) (1.5-x)
O (x+0.25) (1.5-x) (1.75+x)
O (1.75-x) (1.25-x) (x+0.5)
O (x+0.5) (1.75-x) (1.25-x)
O (1-x) (1-x) (1-x)
O (1.5-x) (x+0.75) (x+0.25)
to be used with ibarv = 2 and ATOMIC_POSITIONS alat (not crystal) ,
I didn't test it in QE, please confirm if it works!
Youssef Aharbil,
Laboratory of Physics and Chemistry of Materials
Faculty of sciences Ben msik, Casablanca
Morocco
--
El éxito solo es para los que se arriesgan por sus objetivos.
Máximo Ramírez Mateo
Desarrollador de Software
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