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

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