Phase stability of two-dimensional monolayer As1−xPx solid solutions revealed by a first-principles cluster expansion

Abstract

The phase stability of two-dimensional monolayer As 1−x P x solid solutions, exhibiting the puckered (α phase) and buckled (β phase) structures are investigated using a first-principles cluster-expansion method. Canonical Monte Carlo simulations, together with harmonic approximation, are performed to capture the influences of thermally induced configurational disorder and lattice vibrations on the phase stability of monolayer As 1−x P x. We first demonstrate that, as the temperature approaches 0 K, the monolayer As 1−x P x displays a tendency toward phase separation into its constituent elemental phases, and thus no stable ordered structures of As 1−x P x , both α and β phases, are predicted to be thermodynamically stable. We further reveal with the inclusion of the lattice vibrational contributions that β-As 1−x P x is thermodynamically favored over α-As 1−x P x across the entire composition range even at 0 K and increasingly so at higher temperature, and a continuous series of disordered solid solution of β-As 1−x P x , where 0 x 1, is predicted at the temperature above 550 K. These findings not only indicate that the ordered structures of monolayer α-As 1−x P x and β-As 1−x P x , frequently studied in the literature, may not exist in nature, but also presumably suggest that monolayer α-As 1−x P x is metastable with respect to monolayer β-As 1−x P x .

Phase behaviour of (Ti:Mo) S2 binary alloys arising from electron-lattice coupling

“…Applications range from nanostructured electronics such as FET channels (1,2) to Li-and Na-ions batteries (3,4) and solid lubrication (5)(6)(7). While theoretical and experimental studies tend to focus on the electronic and mechanical properties, the phase behaviour of low dimensional materials, equally important to inform synthesis strategies and understand service life, remains an open question (8).…”

Bimetallic Alloys b-AsxP1–x at High Concentration Differences: Ideal for Photonic Devices

“…The components of b-As x P 1– x can be optimized for specific uses with the alloying strategy. , Due to the tunability of their layer numbers and chemical composition environment, the band gap of bulk b-As x P 1– x can be fully turned over the range from 0.15 to 0.3 eV. Several recent theoretical studies on b-As x P 1– x have also revealed its excellent physicochemical properties. − For example, Shojaei et al investigated the electrical structure in detail and estimated its carriers up to 10 000 cm 2 V –1 s –1 , and Sun et al calculated its lattice thermal conductivity, highlighting the effect of atomic arrangement . Zhu et al calculated the electronic band structures of As x P 1– x and expected a structure transition from α-phase to β-phase at x = 0.93. , Meanwhile, As x P 1– x has been used experimentally in photonics devices such as photodetectors, saturable absorbers, optical logic devices, etc. ,, The broadband nonlinear optical response of As 0.4 P 0.6 nanomaterial has high optical stability by virtue of spatial self phase modulation (SSPM) .…”