Elastic Modulus of Isotopically-Concentrated Lithium

Abstract

The effect of isotopic mass on elastic properties of solids was studied by measuring the elastic modulus of isotopically-concentrated polycrystalline specimens of metallic lithium at 25°C. The elastic modulus of lithium-6 (96.1% ${\mathrm{Li}}^6$, 3.9% ${\mathrm{Li}}^7$) was found to be (7.93±0.21)×${10}^{10}$ dynes/${\mathrm{cm}}^2$, and that of lithium-7 (7.5% ${\mathrm{Li}}^6$, 92.5% ${\mathrm{Li}}^7$) (7.98±0.33)×${10}^{10}$ dynes/${\mathrm{cm}}^2$. Within the limits of precision of the experiments, the values do not differ. It is concluded that isotopic mass has no effect on static elastic properties other than that arising from the change in lattice constants.