First-principles prediction of stabilities and instabilities of compounds and alloys in the ternary B-As-P system

Abstract

We examine the thermodynamic stability of compounds and alloys in the ternary B-As-P system theoretically using first-principles calculations. We demonstrate that the icosahedral B 12 As 2 is the only stable compound in the binary B-As system, while the zinc-blende BAs is thermodynamically unstable with respect to B 12 As 2 and the pure arsenic phase at 0 K, and increasingly so at higher temperature, suggesting that BAs may merely exist as a metastable phase. On the contrary, in the binary B-P system, both zinc-blende BP and icosahedral B 12 P 2 are predicted to be stable. As for the binary As-P system, As 1−x P x disordered alloys are predicted at elevated temperature-for example, a disordered solid solution of up to ∼75 at.% As in black phosphorus as well as a small solubility of ∼1 at.% P in gray arsenic at T = 750 K, together with the presence of miscibility gaps. The calculated large solubility of As in black phosphorus explains the experimental syntheses of black-phosphorus-type As 1−x P x alloys with tunable compositions, recently reported in the literature. We investigate the phase stabilities in the ternary B-As-P system and demonstrate a high tendency for a formation of alloys in the icosahedral B 12 (As 1−x P x ) 2 structure by intermixing of As and P atoms at the diatomic chain sites. The phase diagram displays noticeable mutual solubility of the icosahedral subpnictides in each other even at room temperature as well as a closure of a pseudobinary miscibility gap around 900 K. As for pseudobinary BAs 1−x P x alloys, only a tiny amount of BAs is predicted to be able to dissolve in BP to form the BAs 1−x P x disordered alloys at elevated temperature. For example, less than 5% of BAs can dissolve in BP at T = 1000 K. The small solubility limit of BAs in BP is attributed to the thermodynamic instability of BAs with respect to B 12 As 2 and As.

Ensemble-Based Modeling of the NMR Spectra of Solid Solutions: Cation Disorder in Y2(Sn,Ti)2O7

“…The real system is expected to have lower configurational entropy, and a slightly larger region of immiscibility would be predicted. We have also ignored finite-temperature effects arising from vibrational contributions to the thermodynamics of mixing, which are typically much smaller than configurational effects. , This simplifies the calculations considerably, as we can use the 0 K energies from DFT for the statistical analysis at finite temperature, but this is not expected to substantially affect the results.…”

Thermodynamic consideration and ground-state search of icosahedral boron subselenide B12(B1−xSex)2<

“…The results, observed from the dilute defect study, also indicate a tendency of mixing between B 12 (Se-B) and B 12 2 3 , and 5 6 , by using the superatom-special quasirandom structure (SA-SQS) approach [33][34][35]. For this particular case, two superatomic species, as shown in Fig.…”

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

“…x 1), conducted by Liu et al [18] and Osters et al [42]. On the other hand, a solubility of P atoms in β-arsenic to form a bulk solid solution of β-As 1−x P x is rather small (x < 0.1) even at temperature above the sublimating temperature of the materials [22]. This thus opens up a route to fabricate monolayer α-As 1−x P x in a metastable state from the bulk counterpart by using the exfoliation methods, as demonstrated by Liu et al [18].…”

“…Although α phase of monolayer As 1−x P x is never stable from thermodynamic consideration with respect to β phase, a large solid solubility of As atoms in bulk α-phosphorus to form a bulk solid solution of α-As 1−x P x , in which the arsenic content can be as high as 80 at.% (x ≈ 0.2), was theoretically predicted at elevated temperature [22] and also in line with the experimental syntheses of bulk α-As 1−x P x with highly tunable compositions (0.17…”

“…To the best of our knowledge, the mixing thermodynamics of monolayer As 1−x P x solid solutions, both α and β phases, has so far never been explored. Although the alloying behavior of bulk αand β-As 1−x P x solid solutions was previously reported in the literature [22], recent theoretical investigation of bulk and monolayer As 1−x Sb x solid solutions has revealed that the mixing thermodynamics of As and Sb in the 2D monolayer state is considerably different from that of their 3D bulk counterparts [23]. This highlights an importance of understanding the mixing thermodynamics of monolayer As 1−x P x in order to optimally design the alloy and fully functional it in future applications.…”