## phonopy-users

 [Phonopy-users] Modulation Amplitude From: - 2013-08-07 11:25:31 ```Dear All, I would like to know how the amplitude of atom movement is determined for a modulation. I am using the "MODULATION" keyword to generate modulated structures due to modes at q-vectors (1/2,0,0) and (1/2,1/2,0). For example my input file for the first of these is: ATOM_NAME = Mg Sn O DIM = 2 2 2 MODULATION = 1/2 0 0 2 2 2, 1 20 I find that the dominant atom movement ( which is due to Sn atoms in my system ) is much larger for q=(1/2, 1/2, 0) compared to q=(1/2,0,0) when I use the same amplitude. Can someone explain to me why this occurs? Many thanks, David. -- Dr. David A. Tompsett Materials Chemistry Group Department of Chemistry University of Bath Bath BA2 7AY U.K. Tel: +44 7907 566351 (mobile) Fax: +44 1225 386231 http://people.bath.ac.uk/msi20/ ```
 Re: [Phonopy-users] Modulation Amplitude From: Aldo Humberto Romero - 2013-08-07 12:38:37 ```Well... if these are two points in the Brillouin zone, probably they will have differente energies to excite the same energy mode (that is why we have dispersion), therefore, it is expected that the same phonon branch changes with q, E(q) after all!. -> Dear All, -> -> I would like to know how the amplitude of atom movement is determined -> for a modulation. I am using the "MODULATION" keyword to generate -> modulated structures due to modes at q-vectors (1/2,0,0) and -> (1/2,1/2,0). For example my input file for the first of these is: -> ATOM_NAME = Mg Sn O -> DIM = 2 2 2 -> MODULATION = 1/2 0 0 2 2 2, 1 20 -> -> I find that the dominant atom movement ( which is due to Sn atoms in -> my system ) is much larger for q=(1/2, 1/2, 0) compared to q=(1/2,0,0) -> when I use the same amplitude. Can someone explain to me why this -> occurs? -> -> Many thanks, -> David. -> -- -> -> Dr. David A. Tompsett -> Materials Chemistry Group -> Department of Chemistry -> University of Bath -> Bath BA2 7AY -> U.K. -> Tel: +44 7907 566351 (mobile) -> Fax: +44 1225 386231 -> http://people.bath.ac.uk/msi20/ -> -> -> ------------------------------------------------------------------------------ -> Get 100% visibility into Java/.NET code with AppDynamics Lite! -> It's a free troubleshooting tool designed for production. -> Get down to code-level detail for bottlenecks, with <2% overhead. -> Download for free and get started troubleshooting in minutes. -> http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk -> _______________________________________________ -> Phonopy-users mailing list -> Phonopy-users@... -> https://lists.sourceforge.net/lists/listinfo/phonopy-users -> -- Prof. Aldo Humberto Romero CINVESTAV-Unidad Queretaro Libramiento Norponiente 2000 CP 76230, Queretaro, QRO, Mexico tel: 442 211 9909 fax: 442 211 9938 email: aromero@... aldorome@... www: qro.cinvestav.mx/~aromero ```
 Re: [Phonopy-users] Modulation Amplitude From: Atsushi Togo - 2013-08-08 05:33:56 ```Hi, Mean square displacement is calculated from the number of bosons excited (See http://phonopy.sourceforge.net/thermal-displacement.html#thermal-displacement) But in MODULATION tag, no such thing is considered at all, and you can not compare different phonon modes. Togo On Wed, Aug 7, 2013 at 9:17 PM, Aldo Humberto Romero wrote: > Well... if these are two points in the Brillouin zone, probably they will > have > differente energies to excite the same energy mode (that is why we have > dispersion), therefore, it is expected that the same phonon branch changes > with q, E(q) after all!. > > > -> Dear All, > -> > -> I would like to know how the amplitude of atom movement is determined > -> for a modulation. I am using the "MODULATION" keyword to generate > -> modulated structures due to modes at q-vectors (1/2,0,0) and > -> (1/2,1/2,0). For example my input file for the first of these is: > -> ATOM_NAME = Mg Sn O > -> DIM = 2 2 2 > -> MODULATION = 1/2 0 0 2 2 2, 1 20 > -> > -> I find that the dominant atom movement ( which is due to Sn atoms in > -> my system ) is much larger for q=(1/2, 1/2, 0) compared to q=(1/2,0,0) > -> when I use the same amplitude. Can someone explain to me why this > -> occurs? > -> > -> Many thanks, > -> David. > -> -- > -> > -> Dr. David A. Tompsett > -> Materials Chemistry Group > -> Department of Chemistry > -> University of Bath > -> Bath BA2 7AY > -> U.K. > -> Tel: +44 7907 566351 (mobile) > -> Fax: +44 1225 386231 > -> http://people.bath.ac.uk/msi20/ > -> > -> > -> > ------------------------------------------------------------------------------ > -> Get 100% visibility into Java/.NET code with AppDynamics Lite! > -> It's a free troubleshooting tool designed for production. > -> Get down to code-level detail for bottlenecks, with <2% overhead. > -> Download for free and get started troubleshooting in minutes. > -> > http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk > -> _______________________________________________ > -> Phonopy-users mailing list > -> Phonopy-users@... > -> https://lists.sourceforge.net/lists/listinfo/phonopy-users > -> > > > -- > > Prof. Aldo Humberto Romero > CINVESTAV-Unidad Queretaro > Libramiento Norponiente 2000 > CP 76230, Queretaro, QRO, Mexico > tel: 442 211 9909 > fax: 442 211 9938 > > email: aromero@... > aldorome@... > www: qro.cinvestav.mx/~aromero > > > ------------------------------------------------------------------------------ > Get 100% visibility into Java/.NET code with AppDynamics Lite! > It's a free troubleshooting tool designed for production. > Get down to code-level detail for bottlenecks, with <2% overhead. > Download for free and get started troubleshooting in minutes. > http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk > _______________________________________________ > Phonopy-users mailing list > Phonopy-users@... > https://lists.sourceforge.net/lists/listinfo/phonopy-users -- Atsushi Togo http://atztogo.github.com/ atz.togo@... ```