Dear L.M.,

You need to use sys = sys.finalized() Instead of what you have. The reason for this is that finalized method returns the finalized system, instead of modifying the original system.

Best, Anton

On Sun, Nov 29, 2015, 20:53 L.M J heysuperming@gmail.com wrote:

I was trying to calculate the arm-chair graphene nano ribbon band structure.

I used translational symmetry to define the lead to be infinite, but I still got an error saying "TypeError: Expecting an instance of InfiniteSystem."

I can't identify what's problem here. can anyone help?

Thanks for advance.

code:

l_a=1.0 agnr=kwant.lattice.general([(3*l_a,0),(0,sqrt(3)*l_a)],

[(0,0),(0.5*l_a,sqrt(3)*l_a/2),(1.5*l_a,sqrt(3)*l_a/2),(2*l_a,0)])

a,b,c,d=agnr.sublattices print agnr.vec((-1,0)) ld=kwant.TranslationalSymmetry(agnr.vec((-1,0)))

h=10 w=h

def shape1(pos): x,y=pos return (abs(y)<h and abs(x)<w)

left_lead=kwant.Builder(ld)

left_lead[agnr.shape(shape1,(0,0))]=0

left_lead[[kwant.builder.HoppingKind((0,0),a,b)]]=-2.74 left_lead[[kwant.builder.HoppingKind((0,0),b,c)]]=-2.74 left_lead[[kwant.builder.HoppingKind((0,0),c,d)]]=-2.74

left_lead[[kwant.builder.HoppingKind((-1,0),d,a)]]=-2.74 left_lead[[kwant.builder.HoppingKind((0,1),a,b)]]=-2.74 left_lead[[kwant.builder.HoppingKind((0,1),d,c)]]=-2.74

kwant.plot(left_lead);

left_lead.finalized();

bands=kwant.physics.Bands(left_lead);

mom=np.linspace(-np.pi,np.pi,101) ee=[bands(k) for k in mom] pyplot.plot(mom, ee); pyplot.grid('on') pyplot.ylim(-2.2,2.2)