High-pressure <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Na</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>4</mml:mn></mml:msub><mml:mo>,</mml:mo></mml:mrow></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ca</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>4</mml:mn></mml:msub><mml:mo>,</mml:mo></mml:mrow></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Sr</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>4</mml:mn></mml:msub><mml:mo>,</mml:mo></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Ba</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> featuring nitrogen dimers with noninteger charges and anion-driven metallicity
Dominique Laniel, B. Winkler, Timofey Fedotenko, Alena Aslandukovа, Andrey Aslandukov, Sebastian Vogel, Thomas Meier, Maxim Bykov, Stella Chariton, Konstantin Glazyrin, Victor Milman, Vitali B. Prakapenka, Wolfgang Schnick, Leonid Dubrovinsky, Natalia Dubrovinskaia
Abstract
Charged molecular species, such as ${{[{\mathrm{N}}_{2}]}^{x}}^{\text{--}}$, ${{[{\mathrm{O}}_{2}]}^{x}}^{\text{--}}$, ${{[{\mathrm{C}}_{2}]}^{x}}^{\text{--}}$, and ${{[{\mathrm{S}}_{2}]}^{x}}^{\text{--}}$, follow the paradigm of carrying integer values of electrons. Here, the ${\mathrm{Na}}_{3}{({\mathrm{N}}_{2})}_{4}$, ${\mathrm{Ca}}_{3}{({\mathrm{N}}_{2})}_{4}$, ${\mathrm{Sr}}_{3}{({\mathrm{N}}_{2})}_{4}$, and $\mathrm{Ba}{({\mathrm{N}}_{2})}_{3}$ compounds were produced and characterized 70 GPa and evidenced to be composed of paradigm-breaking ${{[{\mathrm{N}}_{2}]}^{x}}^{\text{--}}$ dimers with noninteger charges of \ensuremath{-}0.75, \ensuremath{-}1.5, \ensuremath{-}1.5, and \ensuremath{-}0.67, respectively. The anion-driven metallicity of the compounds is proposed as the physical mechanism enabling the noninteger electron count of the ${{[{\mathrm{N}}_{2}]}^{x}}^{\text{--}}$ dimers. The properties of these dimers and the compounds bearing them are demonstrated to depend on their noninteger charge, paving the way to materials with electron-tunable features.