Structural stability of beta-beryllium
2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 3, 035132- p.Article in journal (Refereed) Published
Using density-functional theory formulated within the framework of the exact muffin-tin orbitals method, we investigate the stability of the body-centered-cubic phase of Be (β-Be). The elastic constants and Debye temperature of β-Be are calculated over a wide volume range and compared to those obtained for the low-temperature hexagonal phase (α-Be). A significant difference in the anisotropy of the bcc and hcp structures is found. In line with experiments, we predict that the hcp→bcc phase transition occurs at 240 GPa at 0 K and 239 GPa at ambient temperature. We find that the cubic shear constant C′=(C11−C12)∕2 rapidly decreases for volumes above ∼1.05V0, where V0 is the zero temperature equilibrium volume for β-Be. At 1.17V0, the stability condition C′>0 is violated and the bcc phase becomes mechanically unstable. We demonstrate that at 0 K, the softening of β-Be near its experimental volume of 1.063V0 is related to an electronic topological transition due to the increased number of occupied s states near the Fermi level compared to that at V0. This softening turns out to be important for the stability of the bcc phase before melting. The disclosed electronic topological transition is found to be present in other analogous hexagonal metals as well.
Place, publisher, year, edition, pages
2007. Vol. 75, no 3, 035132- p.
IdentifiersURN: urn:nbn:se:uu:diva-23855DOI: 10.1103/PhysRevB.75.035132ISI: 000243895400065OAI: oai:DiVA.org:uu-23855DiVA: diva2:51629