\draw[thick]
(-0.5,0) node[vertex] (n1^4) {}
-- (0.25,2.2) node[vertex] (n2^4) {}
-- (2,1.6) node[vertex] (n3^4) {}
-- (-0.7,1.4) node[vertex] (n4^4) {}
-- (-0.9,1.0) node[vertex] (n5^4) {}
-- (0.8,1.2) node[vertex] (n6^4) {} -- cycle;