-- Define a tight binding Hamiltonian for an infinite 1 dimensional chain
HTB = NewTightBinding()
HTB.Name = "1D tight binding"
HTB.Cell = {{1,0,0},
            {0,1,0},
            {0,0,1}}
HTB.Atoms = { {"A", {0,0,0},       {{"s", {"0"}}} } }
HTB.Hopping = { {"A.s","A.s",{ 0, 0, 1},{{1}} } ,
                {"A.s","A.s",{ 0, 0,-1},{{1}} } }
-- create an operator representing a 10 site supercell with periodic boundary conditions
HCl = CreateClusterHamiltonian(HTB, {"periodic",{{1,0,0},{0,1,0},{0,0,10}}})
-- calculate the vacuum one-particle Green's function for site 0
vacStr=""
for i=1,HCl.NF do
  vacStr=vacStr.."0"
end
psivac = NewWavefunction(HCl.NF,0,{{vacStr,1}})
a0Cr = NewOperator(HCl.NF,0,{{ 0,1}})
S, G = CreateSpectra(HCl,a0Cr,psivac,{{"Tensor",true}})
-- change the one-particle Green's function to different types
GAnd = ResponseFunction.ChangeType(G,"And")
GAnd.Chop(1E-12,{{"deflate",true}})
GAnd.name = "G in Anderson representation"
print("The one particle Green's function is")
print(GAnd)
-- change the Green's function to a tight binding model
HTB2 = Chop( ResponseFunction.ToTightBinding(GAnd) )
print("A tight binding Hamiltonian with the same one particle Green's function is given as")
print(HTB2)