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