The Raiskii graph is the 8-vertex, 18-edge graph illustrated above. It has graph diameter 2 and girth 3.
It is the smallest graph with graph dimension 3 and chromatic number 5 (Nechushtan
2002). Its unit-distance embedding in
gives the lower
bound
,
the
case of Raiskii's general bound
(Raiskii 1970).
The Raiskii graph is implemented in the Wolfram Language as GraphData["RaiskiiGraph"].