## phonopy-users

 [Phonopy-users] BZ for monoclinic centring From: Torsten Weissbach - 2012-11-16 10:30:27 ```Dear Phonopy users, I have a question regarding the Brillouin Zone of monoclinic centered lattices. Because I use Wien2k, any centring must be removed, for example by just transforming the whole cell to P1 symmetry without changing the cell itself. Of course, phonopy determines the true symmetry of the cell for itself. In the monoclinic centered case, the BZ is usually chosen as the reciprocal cell of the centered monoclinic lattice, because if we use the non-centered cell, we end up with just P-1 symmetry. The centring is then included by enlarging the BZ border in two directions to 1 full reciprocal period, instead of 1/2 as would be usual. Because I have the same cell, I would expect now that the BZ for this cell also has this feature, i.e. periodicity of 1 in two directions. But judging from the phonon band structure, all periods seem to be 1/2. So which kind of BZ is used by phonopy (1.5) for a monoclinc centered lattice? Regards, Torsten ```
 Re: [Phonopy-users] BZ for monoclinic centring From: Atsushi Togo - 2012-11-16 13:56:12 ```Hi, In phonopy, there is no concept corresponding to conventional cell (or Bravais lattice, BZ), i.e. no convention of the way to choose the unit cell, but there is only a reciprocal primitive cell, which is automatically determined from the unit cell of your input structure and perhaps with PRIMITIVE_AXIS. Togo On Fri, Nov 16, 2012 at 7:10 PM, Torsten Weissbach wrote: > Dear Phonopy users, > > I have a question regarding the Brillouin Zone of monoclinic centered > lattices. Because I use Wien2k, any centring must be removed, for > example by just transforming the whole cell to P1 symmetry without > changing the cell itself. > Of course, phonopy determines the true symmetry of the cell for itself. > > In the monoclinic centered case, the BZ is usually chosen as the > reciprocal cell of the centered monoclinic lattice, because if we use > the non-centered cell, we end up with just P-1 symmetry. The centring is > then included by enlarging the BZ border in two directions to 1 full > reciprocal period, instead of 1/2 as would be usual. > Because I have the same cell, I would expect now that the BZ for this > cell also has this feature, i.e. periodicity of 1 in two directions. But > judging from the phonon band structure, all periods seem to be 1/2. So > which kind of BZ is used by phonopy (1.5) for a monoclinc centered > lattice? > > Regards, > Torsten > > > ------------------------------------------------------------------------------ > Monitor your physical, virtual and cloud infrastructure from a single > web console. Get in-depth insight into apps, servers, databases, vmware, > SAP, cloud infrastructure, etc. Download 30-day Free Trial. > Pricing starts from \$795 for 25 servers or applications! > http://p.sf.net/sfu/zoho_dev2dev_nov > _______________________________________________ > Phonopy-users mailing list > Phonopy-users@... > https://lists.sourceforge.net/lists/listinfo/phonopy-users -- Atsushi Togo http://atztogo.users.sourceforge.net/ atz.togo@... ```
 Re: [Phonopy-users] BZ for monoclinic centring From: Torsten Weissbach - 2012-11-20 12:56:24 ```Hi Togo, thank you. I am struggling a bit to understand monoclinic centered lattices, so probably I have made a mistake myself. Next I will try to use the PRIMITIVE_AXIS tag to get a the bandstructure for the according primitive cell. If this is set, are the band-points also interpreted within the axes of PRIMITIVE_CELL or with the normal axes from the structure file? Regards, Torsten On Fri, 2012-11-16 at 22:56 +0900, Atsushi Togo wrote: > Hi, > > In phonopy, there is no concept corresponding to conventional cell (or > Bravais lattice, BZ), i.e. no convention of the way to choose the unit > cell, but there is only a reciprocal primitive cell, which is > automatically determined from the unit cell of your input structure > and perhaps with PRIMITIVE_AXIS. > > Togo > > On Fri, Nov 16, 2012 at 7:10 PM, Torsten Weissbach > wrote: > > Dear Phonopy users, > > > > I have a question regarding the Brillouin Zone of monoclinic centered > > lattices. Because I use Wien2k, any centring must be removed, for > > example by just transforming the whole cell to P1 symmetry without > > changing the cell itself. > > Of course, phonopy determines the true symmetry of the cell for itself. > > > > In the monoclinic centered case, the BZ is usually chosen as the > > reciprocal cell of the centered monoclinic lattice, because if we use > > the non-centered cell, we end up with just P-1 symmetry. The centring is > > then included by enlarging the BZ border in two directions to 1 full > > reciprocal period, instead of 1/2 as would be usual. > > Because I have the same cell, I would expect now that the BZ for this > > cell also has this feature, i.e. periodicity of 1 in two directions. But > > judging from the phonon band structure, all periods seem to be 1/2. So > > which kind of BZ is used by phonopy (1.5) for a monoclinc centered > > lattice? > > > > Regards, > > Torsten > > > > > > ------------------------------------------------------------------------------ > > Monitor your physical, virtual and cloud infrastructure from a single > > web console. Get in-depth insight into apps, servers, databases, vmware, > > SAP, cloud infrastructure, etc. Download 30-day Free Trial. > > Pricing starts from \$795 for 25 servers or applications! > > http://p.sf.net/sfu/zoho_dev2dev_nov > > _______________________________________________ > > Phonopy-users mailing list > > Phonopy-users@... > > https://lists.sourceforge.net/lists/listinfo/phonopy-users > > > ```
 Re: [Phonopy-users] BZ for monoclinic centring From: Atsushi Togo - 2012-11-20 13:28:17 ```Hi, > Next I will try to use the PRIMITIVE_AXIS tag to get a the bandstructure > for the according primitive cell. If this is set, are the band-points > also interpreted within the axes of PRIMITIVE_CELL or with the normal > axes from the structure file? Yes. PRIMITIVE_AXIS just transforms the input cell to the smaller cell specified. Then the new cell is used to define the reciprocal lattice vectors. Togo > > Regards, > Torsten > > On Fri, 2012-11-16 at 22:56 +0900, Atsushi Togo wrote: >> Hi, >> >> In phonopy, there is no concept corresponding to conventional cell (or >> Bravais lattice, BZ), i.e. no convention of the way to choose the unit >> cell, but there is only a reciprocal primitive cell, which is >> automatically determined from the unit cell of your input structure >> and perhaps with PRIMITIVE_AXIS. >> >> Togo >> >> On Fri, Nov 16, 2012 at 7:10 PM, Torsten Weissbach >> wrote: >> > Dear Phonopy users, >> > >> > I have a question regarding the Brillouin Zone of monoclinic centered >> > lattices. Because I use Wien2k, any centring must be removed, for >> > example by just transforming the whole cell to P1 symmetry without >> > changing the cell itself. >> > Of course, phonopy determines the true symmetry of the cell for itself. >> > >> > In the monoclinic centered case, the BZ is usually chosen as the >> > reciprocal cell of the centered monoclinic lattice, because if we use >> > the non-centered cell, we end up with just P-1 symmetry. The centring is >> > then included by enlarging the BZ border in two directions to 1 full >> > reciprocal period, instead of 1/2 as would be usual. >> > Because I have the same cell, I would expect now that the BZ for this >> > cell also has this feature, i.e. periodicity of 1 in two directions. But >> > judging from the phonon band structure, all periods seem to be 1/2. So >> > which kind of BZ is used by phonopy (1.5) for a monoclinc centered >> > lattice? >> > >> > Regards, >> > Torsten >> > >> > >> > ------------------------------------------------------------------------------ >> > Monitor your physical, virtual and cloud infrastructure from a single >> > web console. Get in-depth insight into apps, servers, databases, vmware, >> > SAP, cloud infrastructure, etc. Download 30-day Free Trial. >> > Pricing starts from \$795 for 25 servers or applications! >> > http://p.sf.net/sfu/zoho_dev2dev_nov >> > _______________________________________________ >> > Phonopy-users mailing list >> > Phonopy-users@... >> > https://lists.sourceforge.net/lists/listinfo/phonopy-users >> >> >> > > > > ------------------------------------------------------------------------------ > Monitor your physical, virtual and cloud infrastructure from a single > web console. Get in-depth insight into apps, servers, databases, vmware, > SAP, cloud infrastructure, etc. Download 30-day Free Trial. > Pricing starts from \$795 for 25 servers or applications! > http://p.sf.net/sfu/zoho_dev2dev_nov > _______________________________________________ > Phonopy-users mailing list > Phonopy-users@... > https://lists.sourceforge.net/lists/listinfo/phonopy-users -- Atsushi Togo http://atztogo.users.sourceforge.net/ atz.togo@... ```