Colossal Pressure-Induced Softening in Scandium Fluoride
Zhongsheng Wei, Lei Tan, Guanqun Cai, Anthony E. Phillips, Iván da Silva, Mark Kibble, Martin T. Dove
Abstract
The counterintuitive phenomenon of pressure-induced softening in materials is likely to be caused by the same dynamical behavior that produces negative thermal expansion. Through a combination of molecular dynamics simulation on an idealized model and neutron diffraction at variable temperature and pressure, we show the existence of extraordinary and unprecedented pressure-induced softening in the negative thermal expansion material scandium fluoride ${\mathrm{ScF}}_{3}$. The pressure derivative of the bulk modulus $B$, ${B}^{\ensuremath{'}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{\partial}B/\ensuremath{\partial}P{)}_{P=0}$, reaches values as low as $\ensuremath{-}220\ifmmode\pm\else\textpm\fi{}30$ at 50 K, and is constant at $\ensuremath{-}50$ between 150 and 250 K.