  Structural stability of Fe2P is investigated in detail using first-principles
calculations based on density functional theory. While the orthorhombic C23
phase is found to be energetically more stable, the experiments suggest it to
be hexagonal C22 phase. In the present study, we show that in order to obtain
the correct ground state structure of Fe2P from the first-principles based
methods it is utmost necessary to consider the zero-point effects such as
zero-point vibrations and spin fluctuations. This study demonstrates an
exceptional case where a bulk material is stabilized by quantum effects, which
are usually important in low-dimensional materials. Our results also indicate
the possibility of magnetic field induced structural quantum phase transition
in Fe2P, which should form the basis for further theoretical and experimental
efforts.
