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

2*U	-2*t	0	0	Sqrt[6]*t	Sqrt[3]*t	0	0
-2*t	2*U	0	Sqrt[3]*t	0	0	0	0
0	0	0	0	Sqrt[2]*t	0	Sqrt[2]*t	0
0	Sqrt[3]*t	0	U	0	0	-(Sqrt[2]*t)	0
Sqrt[6]*t	0	Sqrt[2]*t	0	U	0	0	Sqrt[2]*t
Sqrt[3]*t	0	0	0	0	U	0	-t
0	0	Sqrt[2]*t	-(Sqrt[2]*t)	0	0	U	0
0	0	0	0	Sqrt[2]*t	-t	0	2*U