Influence of boron vacancies on phase stability, bonding and structure of MB2 (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with AlB2 type structure
2015 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 43, 435702- p.Article in journal (Refereed) Published
Transition metal diborides in hexagonal AlB2 type structure typically form stable MB2 phases for group IV elements (M = Ti, Zr, Hf). For group V (M = V, Nb, Ta) and group VI (M = Cr, Mo, W) the stability is reduced and an alternative hexagonal rhombohedral MB2 structure becomes more stable. In this work we investigate the effect of vacancies on the B-site in hexagonal MB2 and its influence on the phase stability and the structure for TiB2, ZrB2, HfB2, VB2, NbB2, TaB2, CrB2, MoB2, and WB2 using first-principles calculations. Selected phases are also analyzed with respect to electronic and bonding properties. We identify trends showing that MB2 with M from group V and IV are stabilized when introducing B-vacancies, consistent with a decrease in the number of states at the Fermi level and by strengthening of the B-M interaction. The stabilization upon vacancy formation also increases when going from M in period 4 to period 6. For TiB2, ZrB2, and HfB2, introduction of B-vacancies have a destabilizing effect due to occupation of B-B antibonding orbitals close to the Fermi level and an increase in states at the Fermi level.
Place, publisher, year, edition, pages
IOP PUBLISHING LTD , 2015. Vol. 27, no 43, 435702- p.
boride; transition metal; chemical bonding; electronic structure; TiB2; NbB2; MoB2
IdentifiersURN: urn:nbn:se:liu:diva-122410DOI: 10.1088/0953-8984/27/43/435702ISI: 000362574000015PubMedID: 26445165OAI: oai:DiVA.org:liu-122410DiVA: diva2:866341
Funding Agencies|European Research Council under the European Community Seventh Framework Program (FP7)/ERC ; KAW Fellowship program; Swedish Research Council (VR) [642-2013-8020, 621-2012-4425, 2014-5841]; Swedish Foundation of Strategic Research (SSF) Synergy Grant FUNCASE2015-11-022015-11-022015-11-19