Semiconducting cubic titanium nitride in the Th3P4 structure

Metastable nitrogen-rich phases are of technological interest as they may possess a range of useful electronic, optical and mechanical properties. Cubic-Ti${}_{3}$N${}_{4}$ is a long-sought-after metastable phase analogous to other ${M}_{3}$N${}_{4}$ (M = tetravalent metal) compounds that were discovered in the past decade. By marrying first-principles calculations with laser-heated diamond anvil cell experiments, the authors present the first experimental discovery and characterization of cubic-Ti${}_{3}$N${}_{4}$ with high cation coordination number. The new phase is expected to exhibit excellent mechanical properties, but unlike metallic TiN, Ti${}_{3}$N${}_{4}$ is a $s\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}r$ $w\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}h$ $a$ $d\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t$ $b\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d$ $g\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}p$ $n\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}r$ 0.9 eV. The thermodynamic stability and transition pathway to ambient pressure are also evaluated.