H is the Hamiltonian. Here we set µ=0. For grand-canonical calculations add -6µ to the main diagonal.

4*h + U	(I*(I + Sqrt[3])*t)/Sqrt[2]	0	0
((-1 - I*Sqrt[3])*t)/Sqrt[2]	4*h + U	(I/2)*(I + Sqrt[3])*t	0
0	(-I/2)*(-I + Sqrt[3])*t	4*h + U	((1 - I*Sqrt[3])*t)/Sqrt[2]
0	0	((1 + I*Sqrt[3])*t)/Sqrt[2]	4*h