[Pw_forum] scf calculation
Giovanni Cantele
Giovanni.Cantele at na.infn.it
Tue May 26 18:02:48 CEST 2009
Dimpy Sharma wrote:
>
> Hi Quantum espresso user,
>
> I have tried to perform a scf calculation using periodic boundary
> condition, however my calculation stops after first iteration step, is
> it because of overlapping of cell? can anybody suggest me ? The input
> file is given below:
>
>
> &CONTROL
> calculation ='scf'
> restart_mode ='from_scratch'
> outdir = '/sfiwork/dsharma/silane/pasq'
> pseudo_dir = '/sfiwork/dsharma/QE_Pseudos/'
> prefix = '1'
> tstress = .false.
> tprnfor = .true.
> etot_conv_thr = 1.D-4
> forc_conv_thr = 1.D-3
> nstep = 600
> /
> &SYSTEM
> ibrav = 0
> celldm(1) =7.680
> nat = 94
> ntyp = 3
> ecutwfc = 40
> ecutrho = 120
> nbnd = 450
> /
> &ELECTRONS
> diagonalization ='david'
> mixing_mode = 'plain'
> conv_thr = 1.0d-6
> mixing_beta = 0.7
> /
> CELL_PARAMETERS cubic
>
> 1.000000000 0.000000000 0.000000000
> 0.000000000 1.000000000 0.000000000
> 0.000000000 0.000000000 12.000000000
> ATOMIC_SPECIES
> Si 28.08600 Si.pz-vbc.UPF
> H 1.00800 H.pz-vbc.UPF
> O 15.9994 O.pz-rrkjus.UPF
> ATOMIC_POSITIONS angstroms
> O 7.0781 6.9497 27.1761
> O 4.3952 6.9992 27.2391
> O 0.5652 4.5006 27.2372
> O 3.2472 4.5482 27.1701
> O 1.9438 0.0919 27.1630
> O 5.7766 3.7444 27.1486
> O 7.6277 1.8605 27.2622
> O 3.7925 1.9787 27.2580
> O 0.4478 0.5350 25.0261
> O 3.4856 0.6080 25.0468
> O 7.3297 3.2255 25.0426
> O 4.2775 3.2996 25.0202
> O 1.9513 3.9801 24.0193
> O 5.7797 7.5116 24.0552
> O 0.0040 5.7160 24.5904
> O 3.8230 5.7805 24.5911
> O 0.2056 7.2121 22.5056
> O 3.6836 7.2984 22.5163
> O 7.4958 4.2109 22.5160
> O 4.0618 4.2895 22.5067
> O 1.9285 0.3168 20.6977
> O 5.7595 3.4671 20.6962
> O 7.6593 1.8808 21.4706
> O 3.7728 1.9700 21.4647
> O 7.2855 7.3586 19.8746
> O 4.2577 7.4328 19.8968
> O 0.4187 4.0760 19.8952
> O 3.4668 4.1529 19.8704
> O 0.0019 1.9039 18.5887
> O 3.8316 1.9347 18.5904
> H 7.4599 6.0212 27.1358
> H 5.3921 7.0051 27.1349
> H 1.5615 4.4933 27.1304
> H 3.6286 5.4768 27.1339
> H 1.9154 6.4168 5.4186
> H 5.7463 6.4168 5.4186
> H 1.9154 2.5859 5.4186
> H 5.7463 2.5859 5.4186
> H 1.9154 1.2450 5.4186
> H 5.7463 1.2450 5.4186
> H 1.9154 5.0759 5.4186
> H 5.7463 5.0759 5.4186
> Si 3.4277 0.5123 26.6794
> Si 7.2634 3.3235 26.6750
> Si 0.4470 0.4413 26.6627
> Si 4.2778 3.3947 26.6563
> Si 3.5195 4.3107 24.0162
> Si 7.3479 7.1869 24.0233
> Si 0.3727 4.2589 24.0241
> Si 4.2002 7.2396 24.0320
> Si 3.4527 0.4290 21.1515
> Si 7.2869 3.4090 21.1521
> Si 0.3996 0.3623 21.1435
> Si 4.2285 3.4744 21.1412
> Si 7.5663 0.2867 18.3507
> Si 3.9489 0.3177 18.3620
> Si 0.1175 3.5208 18.3617
> Si 3.7409 3.5519 18.3482
> Si 1.9286 7.5732 17.2122
> Si 5.7519 7.6559 16.9682
> Si 1.9219 3.8428 16.9706
> Si 5.7634 3.9249 17.2068
> Si 1.9220 1.8288 15.7617
> Si 5.7548 2.0065 15.7591
> Si 1.9193 5.7818 15.7231
> Si 5.7524 5.7178 15.7201
> Si 0.0066 1.9168 14.4083
> Si 3.8367 1.9161 14.4106
> Si 0.0050 5.7504 14.3813
> Si 3.8343 5.7461 14.3845
> Si 7.6487 0.0094 13.0498
> Si 3.8488 0.0070 13.0529
> Si 0.0177 3.8258 13.0511
> Si 3.8171 3.8244 13.0534
> Si 1.9180 0.0028 11.7170
> Si 5.7477 7.6614 11.6950
> Si 1.9180 3.8318 11.6954
> Si 5.7469 3.8289 11.7177
> Si 1.9154 1.9154 10.3635
> Si 5.7463 1.9154 10.3635
> Si 1.9154 5.7463 10.3635
> Si 5.7463 5.7463 10.3635
> Si 0.0000 1.9154 9.0087
> Si 3.8309 1.9154 9.0087
> Si 0.0000 5.7463 9.0087
> Si 3.8309 5.7463 9.0087
> Si 0.0000 0.0000 7.6539
> Si 3.8309 0.0000 7.6539
> Si 0.0000 3.8309 7.6539
> Si 3.8309 3.8309 7.6539
> Si 1.9154 0.0000 6.2994
> Si 5.7463 0.0000 6.2994
> Si 1.9154 3.8309 6.2994
> Si 5.7463 3.8309 6.2994
> K_POINTS automatic
> 4 1 1 0 0 0
>
> Thanks
>
> Dimpy
>
If you try to use a visualization tool like XCrysDen, you'll discover
that many atoms are (almost) overlapped.
An example: atoms 7 - 8
O 7.6277 1.8605 27.2622
O 3.7925 1.9787 27.2580
You specify the atomic positions in Angstrom. Because you specify both
CELL_PARAMETERS and celldm(1) (which is in atomic units),
the unit cell size along x is 1.0 * 7.680 * 0.529177 A = 4.064 A.
Therefore the x coordinate of the first atom is equivalent to
7.6277-4.064 A = 3.563 A. Therefore the distance between the two atoms
is only .26 A. Similar considerations for many more atom pairs.
More hints:
- not very sure about the setting:
ecutwfc = 40
ecutrho = 120
ecutrho should be at least 4*ecutwfc, larger (6-12 times ecutrho) when
using US pseudo
- you choose a 4x1x1 grid, being a=b maybe one expects that the same
k-point sampling is needed along both x and y directions
Giovanni
--
Dr. Giovanni Cantele
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario di Monte S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
Phone: +39 081 676910
Fax: +39 081 676346
E-mail: giovanni.cantele at cnr.it
giovanni.cantele at na.infn.it
Web: http://people.na.infn.it/~cantele
Research Group: http://www.nanomat.unina.it
Skype contact: giocan74
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