The crystallography of anthracene at 95°K and 290°K

Abstract

X-Ray data, at both 290 °K and 95 °K, of high internal consistency, are reported together with the results of a number of detailed least-squares refinement analyses. The observed bond lengths, with an average estimated standard deviation of 0.008 A, are compared with those predicted theoretically by a number of procedures and previous comparisons and suggestions are examined critically. The expansion coefficients of the crystal are markedly anisotropic and, together with the X-ray diffuse scattering, are discussed in relation to rigid body molecular vibrations and molecular reorientation in the lattice on cooling; this latter feature also provides an explanation for the temperature dependence of the principal crystal diamagnetic susceptibilities.