BETA-SUCCINIC ACID, A CRYSTAL OF EXTREME ELASTIC-ANISOTROPY

Single crystals of monoclinic beta-succinic acid, (CH2)(2)(COOH)(2) po ssess an extreme anisotropy of the longitudinal elastic stiffness. The maximum of 12.56 x 10(10) Nm(-2) is observed along the hydrogen-bonde d infinite chains, the minimum of 0.99 x 10(10) Nm(-2) near a perpendi cular direction within the cleavage plane (010). This anisotropy is th e largest hitherto found in ionic or molecular crystals. The tensor of thermal expansion exhibits a considerable anisotropy, too, in accorda nce with the Grueneisen rule.