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

First-principles prediction of stabilities and instabilities of compounds and alloys in the... 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 B12As2 is the only stable compound in the binary B-As system, while the zinc-blende BAs is thermodynamically unstable with respect to B12As2 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 B12P2 are predicted to be stable. As for the binary As-P system, As1−xPx 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 As1−xPx 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 B12(As1−xPx)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 BAs1−xPx alloys, only a tiny amount of BAs is predicted to be able to dissolve in BP to form the BAs1−xPx 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 B12As2 and As. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review B American Physical Society (APS)

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

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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 B12As2 is the only stable compound in the binary B-As system, while the zinc-blende BAs is thermodynamically unstable with respect to B12As2 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 B12P2 are predicted to be stable. As for the binary As-P system, As1−xPx 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 As1−xPx 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 B12(As1−xPx)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 BAs1−xPx alloys, only a tiny amount of BAs is predicted to be able to dissolve in BP to form the BAs1−xPx 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 B12As2 and As.
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Publisher
American Physical Society (APS)
Copyright
Copyright © ©2017 American Physical Society
ISSN
1098-0121
eISSN
1550-235X
D.O.I.
10.1103/PhysRevB.96.024202
Publisher site
See Article on Publisher Site

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 B12As2 is the only stable compound in the binary B-As system, while the zinc-blende BAs is thermodynamically unstable with respect to B12As2 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 B12P2 are predicted to be stable. As for the binary As-P system, As1−xPx 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 As1−xPx 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 B12(As1−xPx)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 BAs1−xPx alloys, only a tiny amount of BAs is predicted to be able to dissolve in BP to form the BAs1−xPx 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 B12As2 and As.

Journal

Physical Review BAmerican Physical Society (APS)

Published: Jul 17, 2017

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