We report variation of lattice structure in diborides (AB2) with different A atoms to identify the special case of MgB2 showing high Tc superconductivity. High purity MgB2 (Tc~39 K) has been prepared by direct reaction of the elements and the lattice parameters are measured by x-ray diffraction determining the strain e of the B-B distance. The results show that the superconductivity in these intermetallics appear near a critical point in a two variables (strain and charge density) phase diagram at (ec, rc).
@article{arxiv.cond-mat/0102410,
title = {High Tc superconductivity at a critical strain and charge density in diborides},
author = {A. Bianconi and N. L. Saini and D. Di Castro and S. Agrestini and G. Campi and A. Saccone and S. De Negri and M. Giovannini M. Colapietro},
journal= {arXiv preprint arXiv:cond-mat/0102410},
year = {2011}
}