Milan Tomic, Roser Valenti, Harald O. Jeschke
We present uniaxial pressure structural relaxations for CaFe2As2 and
BaFe2Ase2 within density functional theory and compare them with calculations
under hydrostatic pressure conditions as well as available experimental
results. We find that CaFe2As2 shows a unique phase transition from a magnetic
orthorhombic phase to a nonmagnetic collapsed tetragonal phase for both
pressure conditions and no indication of a tetragonal phase is observed at
intermediate uniaxial pressures. In contrast, BaFe2As2 shows for both pressure
conditions two phase transitions from a magnetic orthorhombic to a collapsed
tetragonal phase through an intermediate nonmagnetic tetragonal phase. We find
that the critical transition pressures under uniaxial conditions are much lower
than those under hydrostatic conditions manifesting the high sensitivity of the
systems to uniaxial stress. We discuss the origin of this sensitivity and its
relation to superconductivity.
View original:
http://arxiv.org/abs/1106.5623
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