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 >> ....................................................................... >> ~ >> > >
graphene.fdf
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bandstructure
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