<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; ">Hai-Ping: forgive my poor understanding of you progresses, but let me just you a very simple hint. In order for the program to be able to detect a symmetry operation, it is necessary that the fractional translation associated with it can be represented on the discrete FFT grid. As simple as that. Best wishes - Stefano<DIV><BR><DIV><DIV>On Aug 26, 2006, at 6:57 PM, lan haiping wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><DIV>Dear Eyvaz,</DIV> <DIV> </DIV> <DIV>Thank you for this instructions!</DIV> <DIV> </DIV> <DIV>I just tried the coordinates from NRL-weblink, and didnot find any problems as before.</DIV> <DIV> </DIV> <DIV>But i have another problem want to ask you , which is just a result that i wanna finish </DIV> <DIV>Stefano's exercise assigned last mail.</DIV> <DIV> </DIV> <DIV>I just found that inversion symmetry would not found by pw.x code when the FFT grds are not compatable with fractional translation. Then, I tried to mannually set fft grid by nr1,nr2,nr3 .</DIV> <DIV>Take$(espresso) /examples/example02/si.scf.in for example, when <STRONG>ecutwfc</STRONG> is 18.0Ry, the pw.x would found all Sym Ops, with smallest FFT grids (20,20,20). But when <STRONG>ecutwfc</STRONG> is set to 30.0Ry with (30,30,30) fft grids default, the code gave ""warning: symmetry operation # N not allowed". According to mannual, this warning is mostly related to fractional translation incompatable with the fft grids. So, i tried to reset fft grid respectly with (36,36,36), (40,40,40),(60,60,60) and (54,54,54) , no such warning messages are given for the first 3 situation but same occurs for the last fft grids. I cannot understand this test results, since the userguide states that this warning is due to" <STRONG>FFT grid dimension along that direction is not divisible respectively by 2 or by 3, the symmetry operation will not transform the FFT grid into itself</STRONG>" . Obviously, all grids dimension along x/y/z direction can be divided by 2 or 3. </DIV> <DIV> My understanding is correct or not ? </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV>Regards,</DIV> <DIV>Hai-Ping</DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV><BR><BR> </DIV> <DIV><SPAN class="gmail_quote">On 8/24/06, <B class="gmail_sendername">Eyvaz Isaev</B> <<A onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:eyvaz_isaev@yahoo.com" target="_blank">eyvaz_isaev@yahoo.com </A>> wrote:</SPAN> <BLOCKQUOTE class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Hi,<BR><BR>> I just relaxed Anatase TiO2 with *ibrav= 7 , *<BR>> then output gave that Only 8 symmetry Operations are <BR>> found.<BR>Because of that your setup is not consistent.<BR>Your lattice parameter is<BR>7.1356*0.529177=3.7759954012, but 2 Oxygen atoms have<BR>X-component (in units of alat) of 0.5.<BR>You put 1.888, but, 1.888 is not equal<BR>3.7759954012/2=1.8879977. So, they could not be<BR>considered the same within 10^{-6} which is a default<BR>mismatch (please correct me if I am wrong). For sure<BR>you have to use 7 digits (after point) in such a kind <BR>specific cases, as c/a, b/a (and cosines, presumably).<BR>Besides, your atomic positions are completely<BR>different of these specified in<BR><A onclick="return top.js.OpenExtLink(window,event,this)" href="http://cst-www.nrl.navy.mil/lattice/struk.xmol/c5.pos" target="_blank"> http://cst-www.nrl.navy.mil/lattice/struk.xmol/c5.pos </A><BR>Please use lattice parameters and atomic coordinates<BR>(in Angstrom) as they are in the link, and report what<BR>happens.<BR><BR>I am not sure that it is a good idea to relax a well <BR>known structure if you have a problem with its <BR>symmetry.<BR><BR>Bests,<BR>Eyvaz.<BR><BR>> According to your mail, this structure should have<BR>> 16 Symmetry Operations,<BR>> so<BR>> how can i obtain correct symmetry operations ? <BR>><BR>> Input file is below , thank you in advance ! <BR>><BR>><BR>> *&CONTROL<BR>> title = 'TiO2' ,<BR>> calculation = 'relax',<BR>> verbosity = 'default',<BR>> tprnfor = .true., <BR>> outdir = '/home/haiping/tmp/', <BR>> prefix = 'tio2-1',<BR>> disk_io = 'default',<BR>> nstep = 200,<BR>> pseudo_dir =<BR>> '/home/haiping/espresso/pseudo/', <BR>> /*<BR>><BR>> *&SYSTEM <BR>> ibrav= 7,<BR>> celldm(1)=7.1356,celldm(3)=2.51218,<BR>> nat = 6 ,<BR>> ntyp = 2 ,<BR>> nbnd = 30 , <BR>> ecutwfc = 30.0000000000,<BR>> occupations = 'fixed' ,<BR>> *<BR>><BR>> *&ELECTRONS<BR>> electron_maxstep = 100,<BR>> conv_thr = 1.0e-09,<BR>> mixing_mode = 'plain' , <BR>> startingpot = 'atomic' , <BR>> startingwfc = 'atomic' ,<BR>> mixing_beta = 0.300000000,<BR>> mixing_ndim = 8,<BR>> diagonalization = 'david_overlap' ,<BR>> diago_david_ndim = 8, <BR>> /*<BR>><BR>> *&IONS <BR>> ion_dynamics = 'bfgs',<BR>> pot_extrapolation = 'first_order',<BR>> wfc_extrapolation = 'first_order',*<BR>><BR>> */*<BR>> <BR>> *O 15.999 O.pw91-van_ak.UPF <BR>> Ti 47.867 Ti.pw91-nsp-van.UPF<BR>> ATOMIC_POSITIONS angstrom<BR>> Ti 0.000000000 0.000000000 0.000000000<BR>> Ti 0.000000000 1.888000000 2.371500000 <BR>> O 0.000000000 0.000000000 -1.983097630<BR>> O 0.000000000 0.000000000 1.983097630<BR>> O 0.000000000 1.888000000 0.387796645<BR>> O 0.000000000 1.888000000 4.355203355 <BR>> K_POINTS automatic<BR>> 6 6 7 0 0 0 <BR>> *<BR>> *<BR>><BR>> * On 8/20/06, Eyvaz Isaev <<A onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:eyvaz_isaev@yahoo.com" target="_blank"> eyvaz_isaev@yahoo.com</A>><BR>> wrote:<BR>> ><BR>> > OK, let me hint more.<BR>> ><BR>> > Anatase has a Pearson symbol tI12 or space group <BR>> > I4_1/amd. So, ibrav should be 7, but you have <BR>> chosen a<BR>> > monoclinic lattice, i.e. ibrav=14. The space group<BR>> has<BR>> > 16 symmetry elements, but your choice after<BR>> correcting <BR>> > ecutrho gives only 4 symmetry elements . <BR>> ><BR>> > Imagine FCC lattice and its conventional basis<BR>> > vectors now. According to you now we have to put<BR>> > ibrav=4 or 5. But ibrav=2 for FCC lattice. <BR>> ><BR>> > In addition, I also checked your input file via <BR>> > XCrysDen before I replied previously. Yes, there<BR>> is no<BR>> > problem with it, but a figure does not look like<BR>> > anatase though you used nonzero ibrav. XcrysDen <BR>> > usually replicates atomic positions if <BR>> ibrav.neq.0.<BR>> > For example, if you put ibrav=0 for FCC cell and<BR>> > specify conventional CELL_PARAMETERS you will find<BR>> a<BR>> > rhombohedron, but using ibrav=2 and default basis <BR>> > vectors you find a cubic cell.<BR>> ><BR>> > Bests,<BR>> > Eyvaz.<BR>> ><BR>> ><BR>> > --- lan haiping <<A onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:lanhaiping@gmail.com" target="_blank"> lanhaiping@gmail.com</A>> wrote: <BR>> ><BR>> > > Dear Eyvaz,<BR>> > > Thank you.<BR>> > > I checked the strcuture again using XCRYSDEN,<BR>> > > and found no problems related to the lattices. <BR>> > ><BR>> > > Regards,<BR>> > ><BR>> > > Hai-Ping<BR>> > ><BR>> > ><BR>> > ><BR>> > > On 8/20/06, Eyvaz Isaev <<A onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:eyvaz_isaev@yahoo.com" target="_blank"> eyvaz_isaev@yahoo.com </A>><BR>> > > wrote:<BR>> > > ><BR>> > > > Hi,<BR>> > > ><BR>> > > > It seems your lattice choice is not correct.<BR>> > > Please <BR>> > > > have a look at <BR>> > > ><BR>> <A onclick="return top.js.OpenExtLink(window,event,this)" href="http://cst-www.nrl.navy.mil/lattice/struk/c5.html" target="_blank">http://cst-www.nrl.navy.mil/lattice/struk/c5.html </A><BR>> > > ><BR>> > > > Bests,<BR>> > > > Eyvaz. <BR>> > > ><BR>> > > > --- lan haiping <<A onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:lanhaiping@gmail.com" target="_blank"> lanhaiping@gmail.com</A>> wrote:<BR>> > > ><BR>> > > > > Dear All,<BR>> > > > > I also have calculated gamma phonon <BR>> frequencies<BR>> > > of<BR>> > > > > anatase TiO2 . <BR>> > > > > I run ph.x caculation after relaxing the<BR>> > > structure,<BR>> > > > > but 9 of 18 frequencies <BR>> > > > > are minus.<BR>> > > > ><BR> > > > > > Would you please give me some hints and<BR>> help?<BR>> > > > ><BR>> > > > > input settings are below, thank you in <BR>> advance !<BR>> > > > ><BR> > > > > > *phonons of TiO2 at Gamma<BR>> > > > > &inputph<BR>> > > > > tr2_ph=1.0d-14,<BR>> > > > > recover=.true., <BR>> > > > > epsil=.true., <BR>> > > > > prefix='tio2',<BR>> > > > > fildyn='TiO2-gamma.dyn',<BR>> > > > > outdir='/home/haiping/tmp/'<BR>> > > > > / <BR>> > > > > 0.0 0.0 0.0*<BR>> > > > > **<BR>> > > > > *Relaxing calculation input :*<BR>> > > > > *&CONTROL<BR>> > > > > title = 'TiO2' , <BR>> > > > > calculation = 'relax', <BR>> > > > > verbosity = 'default',<BR>> > > > > tprnfor = .true.,<BR>> > > > > outdir = '/home/haiping/tmp/', <BR>> > > > > prefix = 'tio2', <BR>> > > > > disk_io = 'default',<BR>> > > > > nstep = 200,<BR>> > > > > pseudo_dir =<BR>> > > > > '/home/haiping/espresso/pseudo/', <BR>> > > > > /<BR>> > > > > &SYSTEM<BR>> > > > > ibrav= 14,<BR>> > > > ><BR>> > > > > <BR>> celldm(1)=10.2856,celldm(2)=1.0 ,celldm(3)=1.0,<BR>> > > > ><BR>> > > > > celldm(4)=-0.759357,celldm(5)=-0.759357,<BR>> > > > > celldm(6)=0.518714<BR>> > > > > nat = 6 , <BR>> > > > > ntyp = 2 ,<BR>> > > > > nbnd = 30 ,<BR>> > > > > ecutwfc = 30.0000000000,<BR>> > > > > ecutrho = 160.000,<BR>> > > > > occupations = 'fixed' ,<BR>> > > > > /<BR>> > > > ><BR>> > > > ><BR>> > > > > &ELECTRONS<BR>> > > > > electron_maxstep = 100, <BR>> > > > > conv_thr = 1.0e-07,<BR>> > > > > mixing_mode = 'plain' ,<BR>> > > > > startingpot = 'atomic' ,<BR>> > > > > startingwfc = 'atomic' , <BR>> > > > > mixing_beta = 0.300000000,<BR>> > > > > mixing_ndim = 8,<BR>> > > > > diagonalization = 'david_overlap' ,<BR>> > > > > diago_david_ndim = 8, <BR>> > > > > /<BR>><BR>=== message truncated ===<BR><BR><BR>__________________________________________________<BR>Do You Yahoo!?<BR>Tired of spam? 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