Optimized synthetic Henmilite single-crystal growth

Establish an optimized protocol for targeted synthetic growth of Henmilite single crystals, thereby enabling larger, compositionally controlled specimens for low-temperature inelastic neutron-scattering studies.

Background

Henmilite contains naturally abundant boron and hydrogen, which cause neutron absorption and substantial incoherent background, respectively. Consequently, detailed low-temperature neutron spectroscopy would benefit from larger synthetic crystals with controlled composition. The reported hydrothermal and two-zone thermal-gradient transport experiments did not produce Henmilite crystals, and subsequent measurements relied on naturally grown specimens. Although a related ammonia-evaporation method has produced Henmilite powder, a reproducible single-crystal synthesis procedure remains unavailable.