Abstract
We perform first-principles calculations on CaFeAs under hydrostatic pressure. Our total-energy calculations show that though the striped antiferromagnetic (AFM) orthorhombic (OR) phase is favored at , a nonmagnetic collapsed tetragonal (cT) phase with diminished parameter is favored for GPa, in agreement with experiments. Rather than a mechanical instability, this is an enthalpically driven transition from the higher volume OR phase to the lower volume cT phase. A simple thermodynamic model provides an interpretation of the finite-temperature phase boundaries of the cT phase. Calculations of electronic density of states reveal pseudogaps in both OR and cT phases. Band-structure analysis provides insight into the origin of the pseudogaps while revealing the location and nature of hybridized Fe- and As- bonding orbitals.
- Received 21 May 2013
DOI:https://doi.org/10.1103/PhysRevB.88.045117
©2013 American Physical Society