Microhardness studies on nonlinear optical L-alanine single crystals

Vickers and Knoop microhardness tests were carried out on grown L-alanine single crystals by slow evaporation technique over a load range of 10–50 g on selected broad (2 0 3) plane. Vickers (H v ) and Knoop (H k ) microhardness for the above loads were found to be in the range of 60–71 kg/mm2 and 35–47 kg/mm2, respectively. Vickers microhardness number (H v ) and Knoop microhardness number (H k ) were found to increase with increasing load. Meyer’s index number (n) calculated from H v shows that the material belongs to the soft material category. Using Wooster’s empirical relation, the elastic stiffness constant (c 11) was calculated from Vickers hardness values. Young’s modulus was calculated using Knoop hardness values. Hardness anisotropy has been observed in accordance with the orientation of the crystal.