hi, please read kittel's book. he has an excellent problem for hcp lattice. M is 1/2,0,0 (it bisects the G vector 1,0,0 )and K is 1/3,2/3,0 or 1/3,1/3,0 depending on the gamma angle being 60 or 120 s.auluck
s.auluck > Thanks for your patience. I have anticipated the graphene structure of > Marcos was 2-dimensional and done calculations. I should be more carefull. > Well, I have taken graphene structure this time with four C atoms and seen > the structure and consequently the bandstructure is calculated. The > mismatch of my bandstructure with the reported one happens again. To be > more specific, my question what is the rule for determining coordinates of > K-points like, K, M, Gamma in the reciprocal space. My input fdf > andbandstructures are attached. > > Thanks you > > > On Mon, Sep 17, 2012 at 7:17 PM, Sushil Auluck <[email protected]> wrote: > >> hi, >> in graphene the C atoms are in one plane...therefore it is sometimes >> called 2D material....z=0 for both C atoms... >> try to plot your crystal structure and you will see that you do not get >> the graphene honeycombe.... >> s.auluck >> >> > Many thanks for the reply. It seems that the coordinates of Marcos is >> > true. >> > The coordinates are given in fractional cordinates and distance >> between >> > the two C atoms is ~1.42 Angstrom which is C-C distance in graphene. >> In >> > the >> > prevous post, the bandstructure of Charlier has been wrongly attached. >> > Again I am attaching the input and bandstructures. Sorry for the >> mistake >> > >> > On Mon, Sep 17, 2012 at 4:30 PM, Roland Gillen >> > <[email protected]>wrote: >> > >> >> Hi, >> >> >> >> you might want to check the coordinates of the second carbon atom. >> >> (0.3333, >> >> 0.3333, 0.3333) means that the z-coordinate of the second atom is ~8 >> >> Angstrom, while that of the first is 0 Ang. Marcos probably made a >> typo >> >> in that post you areusing as a reference and meant (0.3333, 0.3333, >> 0.0) >> >> instead of (0.3333, 0.3333, 0.3333). >> >> >> >> Roland >> >> >> >> >> >> >> >> On 17 September 2012 09:08, bedamani singh <[email protected]> >> wrote: >> >> >> >>> I am a new user of siesta and have been trying to find the >> >>> bandstructure >> >>> of graphene. >> >>> >> >>> As the correct selection of K-points in the first brilluion zone is >> a >> >>> prequisite for calculating the bandstructure. I am at loss as how to >> >>> find >> >>> the coordintes of K points in the reciprocal space. I have done >> >>> calculations from the reference ( >> >>> http://www.mail-archive.com/[email protected]/msg00935.html) with the >> >>> atomic positions at (0,0,0); (0.3333, 0.3333, 0.3333) in fractional >> >>> cordinates for C atoms and the lattice cell is used as >> >>> >> >>> LatticeConstant 2.44 Ang >> >>> >> >>> %block LatticeParameters >> >>> >> >>> 1.00 1.00 10.0 90.0 90.0 60.0 >> >>> >> >>> %endblock LatticeParameters >> >>> >> >>> Relaxation was done MD.VariableCell (.true.) and kgrid >> _Monkhorst_Pack >> >>> is used as >> >>> >> >>> %block kgrid_Monkhorst_Pack >> >>> >> >>> 6 0 0 0.0 >> >>> >> >>> 0 6 0 0.0 >> >>> >> >>> 0 0 1 0.0 >> >>> >> >>> %endblock kgrid_Monkhorst_Pack >> >>> >> >>> The coordinates of the Kpoints are calculated using a =1.42 angstrom >> in >> >>> the relations >> >>> >> >>> Gamma= (0,0,0) ; K= (2pi/a)(1/3,0,0) ; and M=(2pi/a)(1/3,1.732/9,0) >> and >> >>> used >> >>> >> >>> BandLinesScale pi/a >> >>> >> >>> %block bandlines >> >>> >> >>> 1 1.476 0.000 0.000 K >> >>> >> >>> 51 0.000 0.000 0.000 /Gamma >> >>> >> >>> 101 1.476 0.852 0.000 M >> >>> >> >>> %endblock bandlines >> >>> >> >>> I am tring to compare the observed bandstructure with those >> reported >> >>> by >> >>> J. C. Charlier et al. (See the attached pdf file)(" Electron and >> phonon >> >>> properties of graphene: their relationship with carbon nanotubes" >> >>> DOI:10.1007/978-3-540-72865-8_21). But the two results are not >> >>> matching. >> >>> The input fdf, my observed bandstructure and bandstructure of J. C. >> >>> Charlier et al. are attached. Anyone please help in finding the true >> >>> K-points. >> >>> >> >>> >> >> >> > >> >> >> ....................................................................... >> Prof. Sushil Auluck Phone:+91-512-6797092/6148 >> Department of Physics +91-512-6798177(Home) >> Indian Institute of Technology Cell :+91-9305548667 >> Kanpur 208016 (UP) Fax :+91-512-6790914 >> India E-mail:[email protected] >> ...............................................:[email protected] >> http://www.iitk.ac.in/phy/People/phy_facvis.html >> http://www.iitk.ac.in/phy/New01/profile_SA.html >> ....................................................................... >> ~ >> > ....................................................................... Prof. Sushil Auluck Phone:+91-512-6797092/6148 Department of Physics +91-512-6798177(Home) Indian Institute of Technology Cell :+91-9305548667 Kanpur 208016 (UP) Fax :+91-512-6790914 India E-mail:[email protected] ...............................................:[email protected] http://www.iitk.ac.in/phy/People/phy_facvis.html http://www.iitk.ac.in/phy/New01/profile_SA.html ....................................................................... ~
