Unistable

24. Are there unistable polyhedra with less than 19 faces? / A unistable polyhedron is one which when made of material of uniform density, will rest in stable equilibrium on only one of its faces.

There are two basic types of amorphous materials—the unistable and the bistable. The unistable material is one in which there are no structural changes. […] The mechanisms for carrier control in the unistable materials are electronic.

(b) What is the least dimension, if any, in which a simplex can be unistable? If the condition of uniform density of material is relaxed, then a simplex can be unistable in 3 dimensions.