Lattices of minimum covolume in Chevalley groups over local fields of positive characteristic

In this article, we show that if G is a simply connected Chevalley group of either classical type of rank bigger than 1 or type E6, and q > 9 is a power of a prime number p > 5, then G = G(F_q((1/t))), up to an automorphism, has a unique lattice of minimum covolume, which is G(F_q[t]).