Single-Crystal X-Ray Diffraction Studies of α-N2 and β-N2

Abstract

The structure of α‐N₂ is cubic in the space group P2₁3 with four molecules per unit cell. A total of 49 independent observed single‐crystal x‐ray diffraction maxima yield ${\mathrm{R=\Sigma \hspace{0.17em}\Vert F}}_o{\mathrm{|-|F}}_c{\mathrm{\hspace{0.17em}\Vert \hspace{0.17em}/\Sigma |F}}_o\text{|=0.13}$ . Two faint reflections, (501) and (520), violate the space group Pa3, which yields R=0.21. Molecular centers are displaced by 0.1 to 0.2 Å from the centrosymmetric positions in Pa3 along the [111] directions so that the symmetry is reduced to P2₁3. Some corrections have been made in the Lorentz factors for upper levels and for the absorption of x rays in the experimental arrangement in the β‐N₂ study. The value of R improves from 0.09 to 0.04 for the freely rotating model, and the best precession angle is 56.0° rather than 54.5° (both ±2.5°) for the precession model, which we prefer.