hi, make sure that the K point ( and nearby points) is included in your k-points list. s.auluck
> Hi, > First of all sorry for repeated questions. The bandstructure with eight > carbon atoms in the unit cell have which has bond length 1.42 Ang is > having > band gap in my calculation. I have viewed the structure and there is > nothing wrong with the structure. I did not take the fractional > coordinates > as I am more convenient with the other. The number of Carbon atoms in the > unit cell have been increased to see other possibilties but in all the > cases the band gap appears. Please anybody tell me where I am making > mistakes. The input and bandstructure plot is attached > > With regards > > > >> >> >> On Tue, Sep 18, 2012 at 8:07 PM, Sushil Auluck <[email protected]> >> wrote: >> >>> 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 >>> ....................................................................... >>> ~ >>> >> >> > ....................................................................... 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 ....................................................................... ~
