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

2*h + U	-t	Sqrt[2]*t	0	0	0	0	0
-t	2*h + U	0	-t	0	0	2*t	t
Sqrt[2]*t	0	2*(h + U)	0	0	0	Sqrt[2]*t	Sqrt[2]*t
0	-t	0	2*(h + U)	-2*t	-(Sqrt[2]*t)	0	0
0	0	0	-2*t	2*(h + U)	0	0	2*t
0	0	0	-(Sqrt[2]*t)	0	2*(h + U)	Sqrt[2]*t	0
0	2*t	Sqrt[2]*t	0	0	Sqrt[2]*t	2*h + U	0
0	t	Sqrt[2]*t	0	2*t	0	0	2*h + U