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

U	0	((3*I)/4)*(I + Sqrt[3])*t	(-I/2)*Sqrt[3]*t	((-3*I)/2)*t	0	0	(-3*(I + Sqrt[3])*t)/4
0	2*U	((3 - I*Sqrt[3])*t)/4	0	0	0	0	((3*I + Sqrt[3])*t)/4
((-3*I)/4)*(-I + Sqrt[3])*t	((3 + I*Sqrt[3])*t)/4	2*U	0	0	-((3*I + Sqrt[3])*t)/4	((-3*I + Sqrt[3])*t)/4	0
(I/2)*Sqrt[3]*t	0	0	U	0	-(Sqrt[3]*t)/2	-((3*I + Sqrt[3])*t)/2	0
((3*I)/2)*t	0	0	0	U	t/2	(-I/2)*(-I + Sqrt[3])*t	0
0	0	-((-3*I + Sqrt[3])*t)/4	-(Sqrt[3]*t)/2	t/2	U	0	((5 - I*Sqrt[3])*t)/4
0	0	((3*I + Sqrt[3])*t)/4	-((-3*I + Sqrt[3])*t)/2	(I/2)*(I + Sqrt[3])*t	0	2*U	(t - (3*I)*Sqrt[3]*t)/4
(-3*(-I + Sqrt[3])*t)/4	((-3*I + Sqrt[3])*t)/4	0	0	0	((5 + I*Sqrt[3])*t)/4	(t + (3*I)*Sqrt[3]*t)/4	2*U