Crystal Structure of Gamma Nitrogen

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 P4₂mnm. At an average pressure and temperature of 4015±{}145 atm and 20.5±{}1.7 K, respectively, the unit cell dimensions are $a=3.957$ {} and $c=5.109$ {}, giving a molar volume of 24.09 cm³ which is in good agreement with the value 24.05 cm³ taken from piston-displacement measurements.