Negative compressibility in a molecular wine rack
Just as we expect materials to expand on increasing temperature, so too is it our intuition that materials should shrink under pressure. The opposite effect — expansion when pressure is applied — is termed negative linear compressibility (NLC) and has only recently been observed experimentally to any significant extent. The material in question, Ag3[Co(CN)6], behaves much like a collapsible wine-rack in that its volume reduces by actually expanding strongly in one direction.
