<div>Thank you for your kindly help!</div>
<div> </div>
<div>It is indeed the problem about sufficiency of digital number for pw.x to find the symmetries. After changing the atom position to satisfy the fractional translation of (0,0,0.5) , pw.x can find all the operation.</div>
<div class="gmail_quote">2009/4/9 Gabriele Sclauzero <span dir="ltr"><<a href="mailto:sclauzer@sissa.it">sclauzer@sissa.it</a>></span><br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Actually the solution was in point (2) of the reply you got by Andrea:<br>
<div class="im"><br> > 2) Your atomic positions are not sufficiently accurate: the number of<br> > digits is sufficient for pw.x to find the symmetries but the<br> > wavefunctions are sufficiently inaccurate to confuse the symmetry<br>
> analyzer. (solution: correct your atomic positions)<br><br></div>If you get your position from a relax calculation, most probably it means that the<br>symmetry of the starting atomic configuration was already C_3v, since during the<br>
relaxations steps the symmetry should be conserved (unless exceptional cases).<br>So please check the initial symmetry in your relax calculation and eventually change the<br>starting configuration.<br>If you don't want to repeat the calculations you can try to fix the atomic positions by<br>
hand. I think that what you are missing to recover the full symmetry is a fractional<br>translation of (0,0,0.5) in crystal axis. For instance, the last two Al are 0.5002 apart<br>along the z direction, instead of 0.500000.<br>
<br>HTH<br><br>GS<br>
<div class="im"><br>程迎春 wrote:<br>> Actually the symmetry of 4H-AlN is C_6v, but the pw.x can not find all<br>> the 12 operations. So I followed the user's guide Page 60, I changed<br>> PW/eqvect.f90. The value of accep is changed to be 10^-3. The changed<br>
> pw.x can find all 12 operations. This change is the reason why you got<br>> C_3v symmetry.<br>><br>> After I rechanged the value of accep to be 10^-5, pw.x only can find 6<br>> operations. Can you give some additional advices to find other operations ?<br>
><br></div>> 2009/4/8 Dal Corso Andrea <<a href="mailto:dalcorso@sissa.it">dalcorso@sissa.it</a> <mailto:<a href="mailto:dalcorso@sissa.it">dalcorso@sissa.it</a>>><br>
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<div class="h5">><br>> On Wed, 2009-04-08 at 19:34 +0800, 程迎春 wrote:<br>> > Dear PWscf users,<br>> > In my recent calculation of 4H-AlN (ABCB stacking sequence),<br>> > the band symmetry seems to be missed in bands.x calculation. The<br>
> > output of bands.x is as following:<br>> ><br>> **************************************************************************<br>> > xk=( 0.00000, 0.00000, 0.00000 )<br>
> > double point group C_6v (6mm)<br>> > there are 9 classes and 3 irreducible representations<br>> > the character table:<br>> > E -E C2 2C3 -2C3 2C6 -2C6 3s_v 3s_d<br>
> > -C2 -3s_v -3s_d<br>> > G_7 2.00 -2.00 0.00 1.00 -1.00 1.73 -1.73 0.00 0.00<br>> > G_8 2.00 -2.00 0.00 1.00 -1.00 -1.73 1.73 0.00 0.00<br>
> > G_9 2.00 -2.00 0.00 -2.00 2.00 0.00 0.00 0.00 0.00<br>> > the symmetry operations in each class:<br>> > E 1<br>> > C2 -C2 2 -2<br>
> > 2C6 3 4<br>> > 2C3 5 6<br>> > 3s_v-3s_v 7 -7 9 10 -10 -9<br>> > 3s_d-3s_d 8 -8 12 -11 11 -12<br>> > -E -1<br>
> > -2C6 -3 -4<br>> > -2C3 -5 -6<br>> > Band symmetry, C_6v (6mm) double point group:<br>> > e( 1 - 2) = -8.01764 eV 2 --> ?<br>
> > e( 3 - 4) = -7.17573 eV 2 --> ?<br>> > e( 5 - 6) = -7.13551 eV 2 --> ?<br>> > e( 7 - 8) = -5.93881 eV 2 --> ?<br>> > e( 9 - 10) = 1.12077 eV 2 --> G_7<br>
> > e( 9 - 10) = 1.12077 eV 2 --> 0 G_8<br>> > e( 11 - 12) = 3.70317 eV 2 --> 0 G_7<br>> > e( 11 - 12) = 3.70317 eV 2 --> G_8<br>
> > e( 13 - 14) = 3.76782 eV 2 --> ?<br>> > e( 15 - 16) = 6.34352 eV 2 --> ?<br>> > e( 17 - 18) = 6.35869 eV 2 --> G_9<br>> > e( 19 - 20) = 6.58061 eV 2 --> ?<br>
> > e( 21 - 22) = 6.59473 eV 2 --> G_9<br>> > e( 23 - 24) = 6.65103 eV 2 --> ?<br>> > e( 25 - 26) = 6.66500 eV 2 --> G_9<br>> > e( 27 - 28) = 6.91040 eV 2 --> ?<br>
> > e( 29 - 30) = 6.92400 eV 2 --> G_9<br>> > e( 31 - 32) = 7.00967 eV 2 --> G_7<br>> > e( 31 - 32) = 7.00967 eV 2 --> 0 G_8<br>
> > e( 33 - 34) = 11.19288 eV 2 --> ?<br>> > e( 35 - 36) = 13.31415 eV 2 --> ?<br>> > e( 37 - 38) = 13.59769 eV 2 --> ?<br>> > e( 39 - 40) = 14.02975 eV 2 --> ?<br>
> > e( 41 - 42) = 17.15974 eV 2 --> ?<br>> > e( 43 - 44) = 17.32327 eV 2 --> ?<br>> > e( 45 - 46) = 17.92003 eV 2 --> ?<br>> ><br>
> **************************************************************************<br>> > My question are :<br>> > 1. what does "?" mean in " e( 1 - 2) = -8.01764 eV 2<br>
><br>> It means that the symmetry finder is confused. The bands have not a<br>> symmetry that it recognizes.<br>> There are several reasons for this:<br>><br>> 1) The 'scf' and 'bands' calculations have been run with slightly<br>
> different parameters. (solution: recheck your input)<br>><br>> 2) Your atomic positions are not sufficiently accurate: the number of<br>> digits is sufficient for pw.x to find the symmetries but the<br>
> wavefunctions are sufficiently inaccurate to confuse the symmetry<br>> analyzer. (solution: correct your atomic positions)<br>><br>> 3) If 1) and 2) do not work and you are sure about your coordinates,<br>
> then probably there is a bug in the symmetry analyzer. (solution: report<br>> to the forum. I will try to solve it if I can).<br>><br>> In your particular case: I am confused. On my PC the symmetry found with<br>
> your coordinates is C_3v and the symmetry analyzer seems to work. So<br>> please recheck your run. If you still find C_6v please recheck your<br>> atomic positions.<br>><br>> Hope this helps.<br>
><br>> Andrea<br>><br>><br>><br>> > --> ?" ?<br>> > 2. what does "0" mean in " e( 9 - 10) = 1.12077 eV 2<br>> > --> 0 G_8" ?<br>
> > 3. In 2H-AlN(AB stacking sequence), all the symmetries of bands are<br>> > shown. Why in 4H-AlN, it seems much more complicated.<br>> ><br>> > The input files about 4H-AlN for pw.x and bands.x are as following:<br>
</div></div>> > <a href="http://scf.in/" target="_blank">scf.in</a> <<a href="http://scf.in/" target="_blank">http://scf.in/</a>><br>
<div>
<div></div>
<div class="h5">> > &control<br>> > title = 2h_aln,<br>> > prefix = '4h_band',<br>> > calculation = 'scf' ,<br>
> > restart_mode = 'from_scratch' ,<br>> > wf_collect = .false. ,<br>> > outdir = './' ,<br>> > wfcdir = './' ,<br>
> > pseudo_dir = './' ,<br>> > tstress = .true. ,<br>> > tprnfor = .true. ,<br>> > wf_collect = .true. ,<br>
> > /<br>> > &SYSTEM<br>> > ibrav = 4,<br>> > celldm(1) = 5.866002785691,<br>> > celldm(3) = 3.238615289089,<br>
> > nat = 8,<br>> > ntyp = 2,<br>> > ecutwfc = 80,<br>> > nbnd = 46,<br>> > nosym = .false. ,<br>
> > lspinorb = .true.,<br>> > noncolin= .true.,<br>> > starting_magnetization=0.00,<br>> > /<br>> > &ELECTRONS<br>
> > electron_maxstep = 100,<br>> > conv_thr = 1.D-10,<br>> > /<br>> > ATOMIC_SPECIES<br>> > N 14.00700 N.rel-pbe-rrkjus.UPF<br>
> > Al 26.98200 Al.rel-pbe-rrkj.UPF<br>> > ATOMIC_POSITIONS (crystal)<br>> > N 0.000000000 0.000000000 -0.000722968<br>> > N 0.000000000 0.000000000 0.499277032<br>
> > N 0.333333333 0.666666667 0.249293699<br>> > N 0.666666667 0.333333333 0.749293699<br>> > Al 0.000000000 0.000000000 0.188800277<br>> > Al 0.000000000 0.000000000 0.688800277<br>
> > Al 0.333333333 0.666666667 0.437593675<br>> > Al 0.666666667 0.333333333 0.937793675<br>> > K_POINTS automatic<br>> > 8 8 8 1 1 1<br>> ><br>
</div></div>> > <a href="http://band.in/" target="_blank">band.in</a> <<a href="http://band.in/" target="_blank">http://band.in/</a>><br>
<div>
<div></div>
<div class="h5">> > &control<br>> > title = 2h_aln,<br>> > prefix = '4h_band',<br>> > calculation = 'bands' ,<br>
> > restart_mode = 'from_scratch' ,<br>> > wf_collect = .false. ,<br>> > outdir = './' ,<br>> > wfcdir = './' ,<br>
> > pseudo_dir = './' ,<br>> > /<br>> > &SYSTEM<br>> > ibrav = 4,<br>> > celldm(1) = 5.866002785691,<br>
> > celldm(3) = 3.238615289089,<br>> > nat = 8,<br>> > ntyp = 2,<br>> > ecutwfc = 80,<br>
> > nbnd=46,<br>> > lspinorb = .true.,<br>> > noncolin= .true.,<br>> > starting_magnetization=0.0,<br>
> > /<br>> > &ELECTRONS<br>> > electron_maxstep = 100,<br>> > conv_thr = 1.D-10,<br>> > /<br>> > ATOMIC_SPECIES<br>> > N 14.00700 N.rel-pbe-rrkjus.UPF<br>
> > Al 26.98200 Al.rel-pbe-rrkj.UPF<br>> > ATOMIC_POSITIONS (crystal)<br>> > N 0.000000000 0.000000000 -0.000722968<br>> > N 0.000000000 0.000000000 0.499277032<br>
> > N 0.333333333 0.666666667 0.249293699<br>> > N 0.666666667 0.333333333 0.749293699<br>> > Al 0.000000000 0.000000000 0.188800277<br>> > Al 0.000000000 0.000000000 0.688800277<br>
> > Al 0.333333333 0.666666667 0.437593675<br>> > Al 0.666666667 0.333333333 0.937793675<br>> > K_POINTS<br>> > 2<br>> > 0.000000 0.000000 0.000000 1.00<br>
> > 0.000000 0.000000 0.083333 1.00<br>> ><br>> ><br></div></div>> > <a href="http://bands.in/" target="_blank">bands.in</a> <<a href="http://bands.in/" target="_blank">http://bands.in/</a>><br>
<div class="im">> > &inputpp<br>> > prefix='4h_band'<br>> > outdir='./'<br>> > filband='spin.dat'<br>> > lsigma(3)=.true.<br>> > lsym=.true.<br>
> > /<br>> ><br>> > Thank you in advance!<br>> ><br>> ><br>> > --<br>> > Y. C. Cheng<br>> > Department of Phyics<br>> > Nanjing University<br>
> > Nanjing 210093<br>> > P. R. China<br>> > Tel: 86-25-83592907<br></div>> > Email: <a href="mailto:yccheng.nju@gmail.com">yccheng.nju@gmail.com</a> <mailto:<a href="mailto:yccheng.nju@gmail.com">yccheng.nju@gmail.com</a>><br>
> ><br>> > _______________________________________________<br>> > Pw_forum mailing list<br>> > <a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a> <mailto:<a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a>><br>
<div class="im">> > <a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>> --<br>> Andrea Dal Corso Tel. 0039-040-3787428<br>
> SISSA, Via Beirut 2/4 Fax. 0039-040-3787528<br>> 34014 Trieste (Italy) e-mail: <a href="mailto:dalcorso@sissa.it">dalcorso@sissa.it</a><br></div>> <mailto:<a href="mailto:dalcorso@sissa.it">dalcorso@sissa.it</a>><br>
><br>><br>> _______________________________________________<br>> Pw_forum mailing list<br>> <a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a> <mailto:<a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a>><br>
<div class="im">> <a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>><br>><br>><br>><br>> --<br>> Y. C. Cheng<br>
> Department of Phyics<br>> Nanjing University<br>> Nanjing 210093<br>> P. R. China<br>> Tel: 86-25-83592907<br></div>> Email: <a href="mailto:yccheng.nju@gmail.com">yccheng.nju@gmail.com</a> <mailto:<a href="mailto:yccheng.nju@gmail.com">yccheng.nju@gmail.com</a>><br>
<div class="im">><br>><br>> ------------------------------------------------------------------------<br>><br>> _______________________________________________<br>> Pw_forum mailing list<br>> <a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>
> <a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br><br>--<br><br><br></div>o ------------------------------------------------ o<br><font color="#888888">| Gabriele Sclauzero, PhD Student |<br>
| c/o: SISSA & CNR-INFM Democritos, |<br>| via Beirut 2-4, 34014 Trieste (Italy) |<br>| email: <a href="mailto:sclauzer@sissa.it">sclauzer@sissa.it</a> |<br>| phone: +39 040 3787 511 |<br>
| skype: gurlonotturno |<br>o ------------------------------------------------ o<br></font>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Y. C. Cheng<br>Department of Physics<br>Nanjing University<br>Nanjing 210093<br>P. R. China<br>Tel: 86-25-83592907<br>Email: <a href="mailto:yccheng.nju@gmail.com">yccheng.nju@gmail.com</a><br>