pot(k,k)=(((-2)/(a*a*dphi*dphi))-(2/(dz*dz)))*(1+(z(zcounter)/L));
            pot(k,k+1)=((1+(z(zcounter)/L))/(a*a*dphi*dphi))+(((1+(z(zcounter)/L))-(1+(z(zcounter)/L)))/4*a*a*dphi*dphi);
            pot(k,k-1)=((1+(z(zcounter)/L))/(a*a*dphi*dphi))-(((1+(z(zcounter)/L))-(1+(z(zcounter)/L)))/4*a*a*dphi*dphi);
            pot(k,k+length(z))=((1+(z(zcounter)/L))/(dz*dz))+(((1+((z(zcounter)+dz)/L))-(1+((z(zcounter)-dz)/L)))/4*dz*dz);
            pot(k,k-length(z))=((1+(z(zcounter)/L))/(dz*dz))-(((1+((z(zcounter)+dz)/L))-(1+((z(zcounter)-dz)/L)))/4*dz*dz);