Pressure dependence of superconducting transition temperature of MgB 2 up to 8 GPa

The pressure dependence of electronic structure, phonon frequencies, electron–phonon coupling constant, and the superconducting transition temperature T c in MgB 2 are calculated via zone‐center frozen phonon modes calculations using the FP‐LAPW method. The calculations are performed from pressure dependent lattice parameters measured experimentally up to 8 GPa. Under quasi‐hydrostatic pressure, T c is found to decrease with an approximately quadratic dependence, deviating significantly from the linearity. It is shown that the pressure‐induced anisotropic change of lattice parameters, the increasing E 2g phonon frequency, and nonlinear electron–phonon coupling are three key factors of producing nonlinear T c ( P ) observed in MgB 2 . (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)