TECHNIQUES FOR NEUTRON-DIFFRACTION ON SOLIDIFIED-GASES TO 10 GPA AND ABOVE - APPLICATIONS TO ND3 PHASE-IV

Neutron powder diffraction can provide important structural informatio n on hydrogenous compounds which are gases at ambient temperature. For high pressure studies, however, this technique has been seriously lim ited by the fact that it was impossible (a) to load such gases in larg e volume devices and (b) to compress them to elevated pressures above some 1 GPa. In this letter we show that, using a previously described pressure cell, a wide range of gaseous samples may be loaded and compr essed to similar to 10 GPa with standard tungsten carbide anvils. We i llustrate the effectiveness of the technique with neutron powder diffr action data recently collected on deuterated ammonia ND3 phase IV, whe re accurate structural data were obtained after a few hours collection time. (C) 1995 American Institute of Physics.