Electronic Structural Properties and Superconductivity of Diborides in the MgB₂ Structure

We calculate the critical temperature T_c of a wide range of diborides which have the same crystal structure as MgB₂. Their electronic structure is also calculated in the framework of the local density approximation method of density functional theory by using the psudopotential plane wave approach. The Hopfield factors η of these materials are calculated by the frozen phonon method. Our results show that most of these diborides have low η, and hence low or no T_c, which are consistent with experimental observations. The most important result of our calculation is that AgB₂ and AuB₂ have higher T_c than MgB₂. The high T_c of these two material comes from the combination of high density of states and high deformation potential of the σ bands.