Phase relations in the Fe-P system at high pressures and temperatures from ab initio computations

ABSTRACT

Based on the first-principles calculations within the density functional theory and crystal structure prediction algorithms iron phosphide phases stable under pressure of the Earth’s core and temperatures up to 4000 K were determined. A new low-temperature modification FeP-P2₁/c stable above ∼75 GPa was predicted. Fe₂P with the allabogdanite structure has been established to be stable in the low-temperature region at ambient conditions. At 750 K it transforms into the barringerite structure. The transition from Fe₃P with schreibersite structure to Fe₃P-Cmcm was observed at 27 GPa, and the phase transition boundary is nearly isobaric. Fe₂P and FeP are thermodynamically stable at the Earth’s inner core pressures and 0 K according to the obtained results, whereas Fe₃P stabilizes with respect to decomposition to Fe + Fe₂P at high temperatures above ∼3200 K.

KEYWORDS:

• Phosphides
• crystal structure prediction
• allabogdanite
• barringerite
• density functional theory

Acknowledgements

The authors are grateful to the Supercomputer Center of the Novosibirsk State University for providing access to the cluster resources.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Nursultan E. Sagatov http://orcid.org/0000-0001-5158-3523

Pavel N. Gavryushkin http://orcid.org/0000-0002-9419-2167

Talgat M. Inerbaev http://orcid.org/0000-0003-2378-4082

Konstantin D. Litasov http://orcid.org/0000-0002-6556-008X

Additional information

Funding

The work was supported by Russian Science Foundation [grant number 17-17-01177].