Transition Metal Ions in Molten Salts: Octahedral Networks and Intermediate-Range Order

Boris Khaykovich
Physics Building Room 120
Deepak Singh

The microscopic structure and dynamics of molten salts is a fascinating subject. It is a very diverse family of materials; while molten NaCl is a simple mix of single-valence ions with a minimal structural organization, transition-metal ions form chains of octahedra, a structural motif present in the solid phases. The interest in molten salts is motivated by both scientific curiosity and practical applications. For example, molten salts are used as coolants in solar power. Molten-salt nuclear reactor (MSR) concepts are candidates for next-generation nuclear power reactors, which promise to be safer and more efficient than existing water-based ones. In these applications, Cr is the principal corrosion product, and NaCl is a common constituent. Therefore, we studied the atomic structure of molten NaCl−CrCl3. We found networks of [CrCl6]3− octahedra and intermediate-range order in remarkable agreement with ab initio simulations. Such studies were enabled and benefited immensely from developments in neutron and X-ray diffraction methods. The availability of Cr isotopes with different neutron scattering properties makes Cr an ideal model multivalent ion for experimental validation of atomistic simulations of molten salts.

Dr. Boris Khaykovich is a Research Scientist at the Nuclear Reactor Laboratory at MIT. Boris received MSc in Chemical Physics and a Ph.D. in Physics (1999) at Weizmann Institute of Science in Israel, followed by postdoctoral training at MIT. Boris is a physicist who has extensive experience in X-ray and neutron scattering methods and instrumentation for materials science. He is known for the development of neutron focusing optics for neutron imaging and small-angle scattering. Boris has been leading projects on the determination of the molecular structure of molten salts and, in the past, conducted crystallographic studies of magnetic and biological materials. Boris has been a Guest Editor of Journal Imaging, Special Issue on Neutron Imaging, and has been the Chair of the SNS/HFIR User Group Executive Committee, representing users of neutron-scattering facilities at Oak Ridge National Lab.