ANISOTROPIC THERMAL PARAMETERS OF NB IN NB3SN

Results of the first complete measurements of Bragg reflections for a monocrystal of Nb3Sn with superconducting transition temperature Tc = 18.2 K have been obtained. A high anisotropy in the vibrations of the atoms along and across the chains of the transition metal suggests a covalent character of the chemical bond between the atoms. For Nb3Sn, the anisotropy is maximum among the superconducting single crystals of the investigated A15 compounds. A correlation between the value of Tc and the degree of anisotropy of the thermal vibrations of the transition metal atoms has been found. © 1979.