Structural changes moving between Isomorphs

The goal of the experiment is to continue our work on the first experimental test of the predictions from isomorph theory,that the structure of a liquid, in reduced units, is invariant along certain lines, isomorphs, in the (P, T)-phase diagram. Isomorph theory predicts that the relaxation time of the liquid is invariant along isomorphs . A previous experiment conducted by the proposer group have shown great agreement with the predictions of isomorph theory for main liquid structure peak of cumene (Isopropylbenzene, C9H12), and the goal of the experiment is to give an microscopic understanding of the changes we see moving between isomorphs. Experimentally we wish to measure on cumene, d-cumene and 50:50 mixture, at four different state points along the ambient pressure isobar. Using isotopic substitution and EPSR to analyze the results. The unique construction of SANDALS (and NIMROD) makes it possible to measure neutron diffraction on both hydrogen-containing as well as deuterated samples.