Crystal Structure of Gamma Nitrogen

Abstract

We have determined by x-ray diffreaction that high-pressure gamma nitrogen is tetragonal with two molecules per unit cell in special position $f$ of space group $\frac{P{4}_{2}}{\mathrm{mnm}}$. At an average pressure and temperature of 4015\ifmmode\pm\else\textpm\fi{}145 atm and 20.5\ifmmode\pm\else\textpm\fi{}1.7 K, respectively, the unit cell dimensions are $a=3.957$ \AA{} and $c=5.109$ \AA{}, giving a molar volume of 24.09 ${\mathrm{cm}}^{3}$ which is in good agreement with the value 24.05 ${\mathrm{cm}}^{3}$ taken from piston-displacement measurements.