[QE-users] problem with number of atoms in pw.x

José Carlos Conesa Cegarra jcconesa at icp.csic.es
Fri Sep 11 14:25:19 CEST 2020


Dear all,

I have found a problem with the number of atoms resulting in a 
computation with pw.x. The essentials of the geometry specification are:

&SYSTEM
   space_group=155, rhombohedral=.TRUE.
   A=8.7018, B=8.7018, C=8.7018
   cosAB=-0.0032742, cosAC=-0.0032742, cosBC=-0.0032742
   nat=13, ntyp=4
...

/

ATOMIC_POSITIONS crystal_sg
V        0.00000    0.00000    0.00000
Ge      -0.75399   -0.99800   -0.74920
N       -0.73084   -0.51728   -0.00123
N       -0.01635   -0.01149   -0.23613
N       -0.52047   -0.23372   -0.50080
N       -0.22951   -0.73368   -0.74864
N       -0.26226   -0.48504   -0.98625
Sn      -0.12491   -0.62544   -0.12283
Ge       0.00000   -0.49511   -0.50488
Ge      -0.50000   -0.75534   -0.24466
Sn      -0.50000   -0.24993   -0.75007
N       -0.76700   -0.76700   -0.76700
Sn      -0.62767   -0.62767   -0.62767

With this input I expect to have 56 atoms, as corresponds to a V-doped 
(Ge,Sn) spinel nitride having almost the same number of Ge and Sn atoms 
(in fact, there is one Sn atom less) as I have verified independently. 
However, I obtain at the beginning of the pw.x calculation the following 
list of atoms:

      site n.     atom                  positions (alat units)
          1           V   tau(   1) = (   0.0000000   0.0000000 0.0000000  )
          2           Ge  tau(   2) = (  -0.0033926  -0.2015179 0.2870436  )
          3           Ge  tau(   3) = (   0.1762159   0.0978209 0.2870436  )
          4           Ge  tau(   4) = (  -0.1728234   0.1036970 0.2870436  )
          5           Ge  tau(   5) = (  -0.0033926   0.2015179 1.4393268  )
          6           Ge  tau(   6) = (   0.1762159  -0.0978209 1.4393268  )
          7           Ge  tau(   7) = (  -0.1728234  -0.1036970 1.4393268  )
          8           N   tau(   8) = (  -0.5167561  -0.1236930 1.0074235  )
          9           N   tau(   9) = (   0.3654993  -0.3856774 1.0074235  )
         10           N   tau(  10) = (   0.1512567   0.5093704 1.0074235  )
         11           N   tau(  11) = (  -0.5167561   0.1236930 0.7189470  )
         12           N   tau(  12) = (   0.3654993   0.3856774 0.7189470  )
         13           N   tau(  13) = (   0.1512567  -0.5093704 0.7189470  )
         14           N   tau(  14) = (   0.1556621   0.0938462 1.5744671  )
         15           N   tau(  15) = (  -0.1591043   0.0878842 1.5744671  )
         16           N   tau(  16) = (   0.0034422  -0.1817305 1.5744671  )
         17           N   tau(  17) = (   0.1556621  -0.0938462 0.1519033  )
         18           N   tau(  18) = (  -0.1591043  -0.0878842 0.1519033  )
         19           N   tau(  19) = (   0.0034422   0.1817305 0.1519033  )
         20           N   tau(  20) = (  -0.0139315   0.2264700 1.0041779  )
         21           N   tau(  21) = (  -0.1891630  -0.1253001 1.0041779  )
         22           N   tau(  22) = (   0.2030945  -0.1011699 1.0041779  )
         23           N   tau(  23) = (  -0.0139315  -0.2264700 0.7221925  )
         24           N   tau(  24) = (  -0.1891630   0.1253001 0.7221925  )
         25           N   tau(  25) = (   0.2030945   0.1011699 0.7221925  )
         26           N   tau(  26) = (   0.3676808  -0.2000458 0.7412862  )
         27           N   tau(  27) = (  -0.0105956   0.4184438 0.7412862  )
         28           N   tau(  28) = (  -0.3570852  -0.2183980 0.7412862  )
         29           N   tau(  29) = (   0.3676808   0.2000458 0.9850842  )
         30           N   tau(  30) = (  -0.0105956  -0.4184438 0.9850842  )
         31           N   tau(  31) = (  -0.3570852   0.2183980 0.9850842  )
         32           N   tau(  32) = (   0.5127756   0.1138545 0.7287873  )
         33           N   tau(  33) = (  -0.3549887   0.3871495 0.7287873  )
         34           N   tau(  34) = (  -0.1577869  -0.5010040 0.7287873  )
         35           N   tau(  35) = (   0.5127756  -0.1138545 0.9975831  )
         36           N   tau(  36) = (  -0.3549887  -0.3871495 0.9975831  )
         37           N   tau(  37) = (  -0.1577869   0.5010040 0.9975831  )
         38           Sn  tau(  38) = (  -0.0014732  -0.4102001 1.2238930  )
         39           Sn  tau(  39) = (   0.3559803   0.2038242 1.2238930  )
         40           Sn  tau(  40) = (  -0.3545071   0.2063759 1.2238930  )
         41           Sn  tau(  41) = (  -0.0014732   0.4102001 0.5024774  )
         42           Sn  tau(  42) = (   0.3559803  -0.2038242 0.5024774  )
         43           Sn  tau(  43) = (  -0.3545071  -0.2063759 0.5024774  )
         44           Ge  tau(  44) = (  -0.3506754   0.2104528 0.5754626  )
         45           Ge  tau(  45) = (  -0.0069197  -0.4089202 0.5754626  )
         46           Ge  tau(  46) = (   0.3575951   0.1984674 0.5754626  )
         47           Ge  tau(  47) = (   0.3575880   0.1984633 0.5754510  )
         48           Ge  tau(  48) = (  -0.0069197  -0.4089120 0.5754510  )
         49           Ge  tau(  49) = (  -0.3506683   0.2104487 0.5754510  )
         50           Ge  tau(  50) = (  -0.1808480   0.3132379 0.8631852  )
         51           Ge  tau(  51) = (   0.3616960  -0.0000000 0.8631852  )
         52           Ge  tau(  52) = (  -0.1808480  -0.3132379 0.8631852  )
         53           Sn  tau(  53) = (   0.1771154  -0.3067729 0.8631852  )
         54           Sn  tau(  54) = (  -0.3542309  -0.0000000 0.8631852  )
         55           Sn  tau(  55) = (   0.1771154   0.3067729 0.8631852  )
         56           N   tau(  56) = (   0.0000000  -0.0000000 0.4022443  )
         57           N   tau(  57) = (  -0.0000000  -0.0000000 1.3241261  )
         58           Sn  tau(  58) = (  -0.0000000  -0.0000000 0.6427795  )
         59           Sn  tau(  59) = (   0.0000000  -0.0000000 1.0835909  )

i.e. there are 3 Ge atoms more than expected (the count for the other 
atoms is OK). And one can see that atoms 44/49, 45/48 and 46/47 are at 
nearly the same positions. But of course with these positions added 
automatically by pw.x the calculation cannot progress. How can this have 
happened? There is something wrong here.

Best regards,

-- 
José C. Conesa
Research Professor
Instituto de Catálisis y Petroleoquímica, CSIC
Marie Curie, 2; Campus de Cantoblanco
28028 Madrid (Spain)
Telef. +34 915854766



More information about the users mailing list