from NanoTCAD_ViDES import *

class UTB(Hamiltonian):
    Lx=3;
    Ly=3;
    a=1;
    def atoms_coordinates(self):
        self.x=self.a*linspace(0,self.n-1,self.n);
        self.y=self.a*linspace(0,self.Nc-1,self.Nc);
        return;

    def gap(self):
        # This is an rough exstimation of 
        # the Energy gap: for sure this is
        # the largest attainable value, within
        # the pz tight-binding model
        return 0;

    def compute_charge_T(self):
        # Number of slices and atoms
        nx=self.n;
        ny=self.Nc;
        me=(0.98*0.19*0.19)**(1/3)*m0;
        thop=hbar**2/(2*me*self.a**2)/q*1e18;
        #Initialization of the list
        h=[];
        #I consider only one orbital
        h.append([1,0,0]);
        #I work on the on-site energies
        for j in range(0,ny):
            for i in range(0,nx):
                ix=i+j*nx;
                h.append([ix+1,ix+1,4*thop]);

        #I work on the hopping parameters
        #First and second off-diagonal
        for j in range(0,ny):
            for i in range(0,nx):
                ix=i+j*nx;
                if (i<nx-1): h.append([ix+1,ix+2,-thop])
                if (j<ny-1): h.append([ix+1,ix+nx+1,-thop])

        self.H=array(h,dtype=complex);
        self.Ei=-self.Phi;
        self.charge_T();
        return;

    def current(self):
        vt=kboltz*self.Temp/q;
        E=array(self.E);
        T=array(self.T);
        arg=2*q*q/(2*pi*hbar)*T*(Fermi((E-self.mu1)/vt)-Fermi((E-self.mu2)/vt))*self.dE
        return sum(arg);