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

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