First-principles calculations on Generalized-stacking-fault energy surface and third-order elastic constants of intermetallics TbCu and TbZn

Generalized-stacking-fault energies (GSFEs) and third-order elastic constants (TOECs) for the rare-earth intermetallic compounds TbCu and TbZn with B2-type structure have been presented from first-principles. Using a slab calculation, we obtained the GSFE curves along {110}, {110} and {110} directions. It is found that there is a energy minimum at 1/2 in the GSFE curves of TbZn called antiphase boundary (APB) energy which is different from TbCu. Basing on the nonlinear elasticity theory which takes not only the second-order elastic constants (SOECs) into account, but also the higher-order elastic constants such as third-order elastic constants (TOECs), we applied six kinds of particular strain, and obtained the TOECs and SOECs. One can see that when the Lagrangian strain reach to 8%, the difference of strain energy values can reach to 15% approximately while the TOECs are taken into account or not.