We have recently identified metal-sandwich (MS) crystal structures and shown with ab initio calculations that the MS lithium monoboride phases are favored over the known stoichiometric ones under hydrostatic pressure [Phys. Rev. B 73, 180501(R) (2006)]. According to previous studies synthesized lithium monoboride tends to be boron-deficient, however the mechanism leading to this phenomenon is not fully understood. We propose a simple model that explains the experimentally observed off-stoichiometry and show that compared to such boron-deficient phases the MS-LiB compounds still have lower formation enthalpy under high pressures. We also investigate stability of MS phases for a large class of metal borides. Our ab initio results suggest that MS noble metal borides are less unstable than the corresponding AlB2-type phases but not stable enough to form under equilibrium conditions.
@article{arxiv.cond-mat/0607654,
title = {Theoretical study of metal borides stability},
author = {Aleksey N. Kolmogorov and Stefano Curtarolo},
journal= {arXiv preprint arXiv:cond-mat/0607654},
year = {2007}
}