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Abstract:
This study addresses the structural and electronic properties of the
NiAs-and MnP-type phases dominating in FeSe at high pressures. The
analysis is performed using first-principle band structure calculations
within the framework of the B3LYP hybrid exchange-correlation
functional. Based on the volume-pressure relation deduced from the
available experimental data, we optimize the form and internal
coordinates of the unit cell, which agree reasonably well with
experiment. In particular, the present calculations resolve the
structural NiAs-MnP phase transition which occurs at about 10 GPa. Both
structures are found to be semiconducting at low pressures and
metallizing at about 80-90 GPa. Using the complementary LDA + U approach
the semiconducting state can be explained as the result of the strong
local correlations within the Fe d-shell.
