[Q-e-developers] average electrostatic potential on amorphous slabs in vacuum

[Saiz, Fernan]

Dear QE developers,

I am using Quantum Espresso 6.2 to model amorphous polyethylene slabs in 
vacuum (see attached input script scf.sh). These slabs are periodic in 
the y and z directions and the surface normal vector is in the x direction.

When I plot the averaged electrostatic potential <V(x)> in the x 
direction using the following script:

&inputpp
   prefix='ape',
   outdir = './tmp/',
   filplot = './pp/data_ape_elect_pot.dat',
   plot_num = 11,
   kpoint = 1,
/
&plot
   nfile=1,
   filepp(1)='./pp/data_ape_elect_pot.dat',
   iflag=3
   output_format=6
   fileout='./pp/data_ape_elect_pot.cube'
/

I see that the electrostatic potential does not plateau at a flat, but 
instead shows a large sinusoidal shape (see attached plot in 
figure.png). In principle, I would expect a non-zero flat because of the 
dipole moments that are created in the amorphous surfaces.

Hence, my question is given the large size of my system and its total 
lack of nuclei symmetry, should I need an even wider vacuum gap to have 
<V(x)> showing a flat profile away from the slab from which I could 
obtain a meaningful vacuum level to correct the eigenvalues? Or do I 
need to implement something else? The dipole correction implemented in 
my input script seems to help little.


Best regards,
  - Fernan Saiz
Postdoctoral research associate
Department of Chemistry
Imperial College London
-------------- next part --------------
&control
  calculation = 'scf',
  restart_mode = 'from_scratch',
  prefix='ape',
  tstress = .true.,
  tprnfor = .true.,
  pseudo_dir = '/home/fsaizpoy/scripts/qe/pseudopotentials/',
  outdir = './tmp/',
  wf_collect = .false.,
  memory = 'small',
  disk_io = 'low',
  verbosity = 'high',
  tefield = .true.
  dipfield = .true.
  /
&system
  ibrav = 0, nat = 240, ntyp= 2,
  ecutwfc = 100.0,
  nbnd = 300,
  london = .true. ,
  london_rcut =  12.2265271461,
  london_s6 = 1.0 ,
  input_dft = 'bp',
  edir = 1
  emaxpos = 0.5
  eopreg = 0.1
  eamp = 0.005
  /
&electrons
  diagonalization = 'david',
  mixing_mode = 'plain',
  mixing_beta = 0.7,
  conv_thr = 1.0d-6,
  /
ATOMIC_SPECIES
C 12.01070 C.bp-van_ak.UPF
H  1.00794 H.bp-van_ak.UPF
K_POINTS (automatic)
 1  1  1  0  0  0
CELL_PARAMETERS { angstrom }
32.94 0.0 0.0
0.0 12.94 0.0
0.0 0.0 12.94
ATOMIC_POSITIONS { angstrom }
C 2.300132 3.806711 7.417048
C 2.516384 2.379284 6.897977
H 3.112608 4.041395 8.147028
H 1.36786 3.824524 8.029863
H 1.745367 2.150826 6.120605
H 2.316476 1.66549 7.733383
C 3.905096 2.08435 6.324096
C 5.038826 2.013086 7.347817
H 3.868709 1.125372 5.749307
H 4.154064 2.859864 5.553643
H 4.935445 1.088366 7.966858
H 4.941655 2.862233 8.067064
C 6.407247 2.086008 6.6767
C 7.64244 2.302011 7.549082
H 6.561162 1.182579 6.039881
H 6.364736 2.936028 5.949603
H 7.968823 1.348044 8.031617
H 7.389591 2.982598 8.402216
C 8.809843 2.920402 6.771709
C 10.055118 3.235447 7.62057
H 9.077391 2.260084 5.910085
H 8.439567 3.861732 6.293669
H 10.840333 2.462379 7.462373
H 9.776231 3.1488 8.701951
C 10.649263 4.634139 7.410535
C 9.689052 5.745731 7.835537
H 11.589252 4.716624 8.006787
H 10.953877 4.767997 6.344602
H 9.166298 5.404711 8.766867
H 8.878228 5.849484 7.077424
C 10.277525 7.118951 8.123681
C 9.247921 8.051885 8.770187
H 11.149898 7.001963 8.809008
H 10.685728 7.578957 7.190863
H 9.760289 8.891663 9.296463
H 8.728381 7.479008 9.579565
C 8.187117 8.637511 7.827542
C 6.908637 9.058127 8.554578
H 8.612283 9.518012 7.28863
H 7.947551 7.899954 7.019685
H 7.194044 9.724275 9.399197
H 6.461768 8.164797 9.055134
C 5.852323 9.778831 7.711282
C 5.012058 8.917692 6.759542
H 5.159857 10.335316 8.392063
H 6.37058 10.57178 7.117361
H 5.686969 8.176455 6.270852
H 4.648702 9.572944 5.932339
C 3.832231 8.190604 7.405271
C 2.806519 7.518703 6.4615
H 4.239694 7.423917 8.097672
H 3.296049 8.907059 8.071122
H 3.313766 7.169632 5.531786
H 2.099005 8.297499 6.095456
C 2.003 6.328487 7.043906
C 2.225142 4.942538 6.392696
H 2.207231 6.250335 8.136022
H 0.916521 6.564294 7.002263
H 3.154999 4.955999 5.778455
H 1.41075 4.7237 5.661114
C 1.950004 4.352377 1.337969
C 2.079488 3.735666 2.732411
H 1.861755 5.458854 1.466478
H 0.985574 4.03032 0.877142
H 1.351165 4.244232 3.407101
H 3.080486 3.99924 3.15921
C 1.858015 2.225578 2.871896
C 2.807704 1.297892 2.086666
H 1.922186 1.983218 3.960493
H 0.8056 1.984954 2.583819
H 3.129423 0.457256 2.743368
H 3.752584 1.847863 1.851978
C 2.230708 0.719472 0.791241
C 3.307076 0.14091 12.806424
H 1.471372 12.877819 1.040047
H 1.668071 1.516431 0.248991
H 4.047889 0.947304 12.580804
H 2.860776 12.816211 11.81588
C 4.051577 11.870872 0.427803
C 5.302035 11.499163 12.581029
H 4.351073 12.075028 1.485549
H 3.358937 10.996062 0.492474
H 5.953312 12.405287 12.52761
H 5.046928 11.25754 11.52082
C 6.085617 10.359524 0.285874
C 7.423684 9.977111 12.59474
H 6.266985 10.643636 1.350879
H 5.437204 9.449738 0.338772
H 7.244215 9.410554 11.647436
H 7.918229 9.246194 0.338175
C 8.372054 11.14425 12.290729
C 8.321589 11.507337 10.809549
H 8.113299 12.030534 12.926425
H 9.422955 10.889932 12.567983
H 7.255835 11.683452 10.517669
H 8.634556 10.601869 10.236768
C 9.179083 12.678319 10.35289
C 8.823686 1.073266 10.997528
H 10.255574 12.452908 10.545352
H 9.086263 12.770937 9.243336
H 9.405598 1.889645 10.499879
H 9.175585 1.082365 12.060498
C 7.349376 1.433152 10.995604
C 7.127408 2.809539 11.581013
H 6.91612 1.357751 9.968469
H 6.787803 0.685784 11.604624
H 7.395349 3.602375 10.840024
H 7.852597 2.949571 12.423627
C 5.73928 3.035982 12.147818
C 5.601342 4.374634 12.865624
H 4.95964 2.920755 11.353697
H 5.533469 2.215 12.881613
H 5.472677 5.195941 12.121103
H 6.564209 4.594213 0.448519
C 4.474921 4.395406 0.941799
C 3.101705 4.095612 0.360267
H 4.713196 3.656924 1.749202
H 4.446608 5.381193 1.460546
H 3.076936 3.045847 12.921701
H 2.94659 4.733504 12.393822
C 11.496664 2.627839 12.629521
C 10.754898 3.908834 12.227334
H 12.596853 2.781026 12.533421
H 11.246811 1.850299 11.868688
H 9.66637 3.669609 12.154563
H 11.043762 4.166516 11.179797
C 10.935011 5.17286 0.143732
C 10.462582 5.096191 1.603266
H 12.009757 5.471255 0.136266
H 10.395677 6.003349 12.569466
H 10.580959 6.101209 2.076188
H 11.149921 4.430831 2.173708
C 9.028659 4.596908 1.800232
C 8.77118 3.904204 3.145779
H 8.299101 5.431399 1.661752
H 8.77728 3.876391 0.984777
H 8.663443 4.674467 3.94775
H 9.682788 3.320156 3.432506
C 7.569376 2.951288 3.161076
C 7.82834 1.635185 2.436561
H 7.277779 2.740076 4.217082
H 6.679284 3.456458 2.70452
H 8.667117 1.095152 2.945116
H 8.212568 1.846364 1.40641
C 6.61588 0.717257 2.299512
C 6.03361 0.145833 3.592732
H 5.804099 1.271808 1.765002
H 6.880729 12.8143 1.613501
H 5.119808 12.494141 3.334586
H 5.66138 0.980817 4.23337
C 6.981362 12.196794 4.392704
C 7.421457 10.929452 3.665852
H 7.890274 12.777963 4.696834
H 6.490077 11.908854 5.357017
H 7.948682 11.200464 2.717273
H 6.51493 10.3622 3.333042
C 8.30225 10.00001 4.496225
C 9.104616 8.986997 3.664902
H 9.002627 10.605462 5.121912
H 7.650349 9.468124 5.229837
H 8.57107 8.814354 2.695298
H 9.101431 7.993801 4.174962
C 10.567517 9.34901 3.377876
C 10.862157 10.635397 2.587928
H 11.113103 9.408551 4.351937
H 11.027027 8.488981 2.835447
H 10.281238 10.636096 1.631053
H 11.934192 10.604174 2.276739
C 10.621756 11.938999 3.342426
C 11.308785 0.237801 2.775978
H 9.527325 12.143703 3.403015
H 10.95101 11.809452 4.40137
H 12.408206 0.180423 2.959951
H 10.965846 1.114203 3.380355
C 11.082114 0.57428 1.294341
C 11.167232 2.088801 1.087995
H 11.821076 0.03806 0.653714
H 10.07972 0.203504 0.959299
H 11.911673 2.490786 1.815324
H 10.196003 2.508863 1.432937
C 4.213926 7.621098 2.604665
C 3.691361 9.057037 2.514863
H 4.670925 7.339998 1.624361
H 3.351341 6.919219 2.742808
H 3.142942 9.192121 1.551214
H 4.562416 9.755539 2.445782
C 2.806494 9.490292 3.669722
C 2.460555 10.975707 3.680698
H 1.86933 8.880497 3.683684
H 3.318745 9.243333 4.625921
H 1.933902 11.252973 2.735176
H 3.417823 11.557935 3.660362
C 1.639356 11.430349 4.888936
C 2.354238 11.279369 6.229944
H 1.351385 12.5025 4.752283
H 0.676133 10.865264 4.920277
H 3.336517 11.81818 6.18728
H 2.618046 10.208746 6.403329
C 1.563916 11.789767 7.430755
C 2.295851 11.577249 8.766901
H 1.338561 12.869879 7.271837
H 0.568903 11.283964 7.46527
H 2.197798 12.476346 9.421476
H 3.393642 11.5006 8.559918
C 1.860655 10.346889 9.560921
C 2.881946 9.990892 10.638593
H 0.860499 10.52367 10.02319
H 1.707005 9.485442 8.864044
H 2.979905 10.871048 11.313899
H 3.887629 9.888546 10.155504
C 2.597911 8.750154 11.486294
C 2.8131 7.406738 10.782192
H 3.249046 8.780535 12.396848
H 1.55174 8.803963 11.869378
H 2.243358 7.397469 9.81955
H 2.359922 6.589054 11.394153
C 4.273789 7.043829 10.497202
C 4.379415 5.701931 9.764343
H 4.76508 7.862752 9.921816
H 4.838757 6.994602 11.462821
H 3.678336 5.715141 8.901146
H 3.945821 4.926271 10.44354
C 5.744897 5.194805 9.277964
C 6.322 5.608508 7.909376
H 6.518444 5.461139 10.042253
H 5.712317 4.079083 9.311538
H 7.25521 5.01425 7.79039
H 6.681512 6.661029 7.960603
C 5.518434 5.464288 6.616946
C 6.362841 5.755591 5.369
H 5.085198 4.440444 6.534049
H 4.643415 6.144786 6.635117
H 7.098092 4.922852 5.245114
H 6.997682 6.662685 5.551333
C 5.583593 5.949773 4.053946
C 5.223878 7.403257 3.734882
H 6.167278 5.520704 3.203549
H 4.645634 5.335742 4.08963
H 6.161208 7.977827 3.519253
H 4.815296 7.878336 4.648729
-------------- next part --------------
A non-text attachment was scrubbed...
Name: figure.png
Type: image/png
Size: 125396 bytes
Desc: not available
URL: <http://lists.quantum-espresso.org/pipermail/developers/attachments/20171214/9d91b641/attachment.png>