Configurational order-disorder induced metal-nonmetal transition in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>B</mml:mtext><mml:mn>13</mml:mn></mml:msub><mml:msub><mml:mtext>C</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>studied with first-principles superatom-special quasirandom structure method

Ektarawong, Annop; Simak, Sergey; Hultman, Lars; Birch, Jens; Alling, Björn

doi:10.1103/physrevb.92.014202

Cited by 22 publications

(31 citation statements)

References 53 publications

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“…We find that the calculated E defect falls into a range between 2.4 and 9.6 eV for B 12 P 2 , whiles it ranges from 2.8 to 10.4 eV for B 12 As 2 . Also, the lowest E defect of the subpnictides are found to be relatively high, as compared to those of boron carbides, i.e., 0.23 eV and 0.6 eV for B 4 C [34] and B 13 C 2 [35], respectively. We thus conclude that configurational disorder at the atomic level, induced by the substitutional defects, is highly unlikely for the two boron subpnictides.…”

Section: Mixing Thermodynamics Of Alloys Between Icosahedral B 12 mentioning

confidence: 85%

“…In this case, all B atoms fully occupy the boron sublattice, while As and P atoms are randomly distributed due to the use of the SQS method on the pnictide sublattice. For modeling the mixing alloys between B 12 As 2 and B 12 P 2 , we employ a superatom special quasirandom structure (SA-SQS) method [34][35][36], designed for modeling configurational disorder in icosahedral boronrich solids, e.g., boron carbide and boron suboxide, whose crystal structures are analogous to those of boron subpnictides. The SA-SQS models of the mixing alloys include 504 atoms (4×3×3 supercells) and the composition x = 0.167, 0.333, 0.50, 0.667, and 0.833.…”

Section: A Computational Detailsmentioning

confidence: 99%

“…To start with, we explore a possibility for the two subpnictides to configurationally disorder, that is, substitution of As and P atoms from the diatomic chains for the icosahedral B atoms. Configurational disorder in icosahedral boron-rich solids has recently been highlighted, especially for boron carbide, as it has been predicted to play an important role to the stability and the properties of the material at elevated temperature [34][35][36]. We consider different kinds of B/P and B/As substitutional defects in the dilute limit, typically involved with only 2 or 4 atoms, in a fully relaxed 2×2×2 supercell of B 12 P 2 and B 12 As 2 , respectively.…”

Section: Mixing Thermodynamics Of Alloys Between Icosahedral B 12 mentioning

confidence: 99%

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

2017

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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.

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Section: Mixing Thermodynamics Of Alloys Between Icosahedral B 12 mentioning

confidence: 85%

Section: A Computational Detailsmentioning

confidence: 99%

Section: Mixing Thermodynamics Of Alloys Between Icosahedral B 12 mentioning

confidence: 99%

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

2017

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“…By performing the Rietveld analysis of the diffraction patterns obtained from x-ray powder diffraction, they proposed that the subnitride has a stoichiometric composition of B 13 N 2 (13.33 at. % N), whose crystal structure is similar to that of B 6 N but the N-N units are replaced by NBN intericosahedral chains, in an analogy to the idealized picture of B 13 C 2 composition of boron carbide [36][37][38][39]. The structural unit of B 13 N 2 is thus given by B 12 (NBN), as shown in Fig.…”

Section: Introductionmentioning

confidence: 95%

“…In the present work, a structural model of B 38 N 6 , proposed as a stable composition in Ref. [34], is achieved as a disordered [B 12 (N − N)] 0.33 [B 12 (NBN)] 0.67 alloy using the superatom-special quasirandom structure (SA-SQS) approach for modeling configurational disorder in boron carbide [39,47] as well as mixing alloys between boron carbide and boron suboxide [48]. The model is constructed within a 3 × 2 × 2 supercell (176 atoms), where two types of superatoms, (1) B 12 (NBN) and (2) B 12 (N-N), are randomly distributed on the lattice sites with a ratio of 2 to 1, and thus represented by [B 12 A detailed investigation of the configuration of the two superatom types in B 38 N 6 , beyond the mean-feld approximation, is also performed using the cluster expansion method, and it will be discussed in Sec.…”

Section: A Computational Detailsmentioning

confidence: 99%

Thermodynamic stability and properties of boron subnitrides from first principles

2017

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We use the first-principles approach to clarify the thermodynamic stability as a function of pressure and temperature of three different α-rhombohedral-boron-like boron subnitrides, with the compositions of B 6 N, B 13 N 2 , and B 38 N 6 , proposed in the literature. We find that, out of these subnitrides with the structural units of B 12 (N-N), B 12 (NBN), and [B 12 (N − N)] 0.33 [B 12 (NBN)] 0.67 , respectively, only B 38 N 6 , represented by [B 12 (N − N)] 0.33 [B 12 (NBN)] 0.67 , is thermodynamically stable. Beyond a pressure of about 7.5 GPa depending on the temperature, also B 38 N 6 becomes unstable, and decomposes into cubic boron nitride and α-tetragonalboron-like boron subnitride B 50 N 2 . The thermodynamic stability of boron subnitrides and relevant competing phases is determined by the Gibbs free energy, in which the contributions from the lattice vibrations and the configurational disorder are obtained within the quasiharmonic and the mean-field approximations, respectively. We calculate lattice parameters, elastic constants, phonon and electronic density of states, and demonstrate that [B 12 (N − N)] 0.33 [B 12 (NBN)] 0.67 is both mechanically and dynamically stable, and is an electrical semiconductor. The simulated x-ray powder-diffraction pattern as well as the calculated lattice parameters of [B 12 (N − N)] 0.33 [B 12 (NBN)] 0.67 are found to be in good agreement with those of the experimentally synthesized boron subnitrides reported in the literature, verifying that B 38 N 6 is the stable composition of α-rhombohedral-boron-like boron subnitride.

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Local Atomic Arrangements and Band Structure of Boron Carbide

Rasim

Ramlau²,

Leithe‐Jasper³

et al. 2018

Angewandte Chemie

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Boron carbide,the simple chemical combination of boron and carbon, is one of the best-known binary ceramic materials.D espite that, ac oherent description of its crystal structure and physical properties resembles one of the most challenging problems in materials science.B yc ombining ab initio computational studies,p recise crystal structure determination from diffraction experiments,a nd state-of-the-art high-resolution transmission electron microscopyimaging,this concerted investigation reveals hitherto unknown local structure modifications together with the knowns tructural alterations.T he mixture of different local atomic arrangements within the real crystal structure reduces the electron deficiency of the pristine structure CBC + B 12 ,a nswering the question about electron precise character of boron carbide and introducing new electronic states within the band gap,w hicha llow abetter understanding of physical properties.The binary phase in the system boron-carbon, with al arge and temperature-dependent complex shape of the homogeneity range between 8.6 and 18.8 at %ofcarbon, is known as boron carbide. [1,2] Preparation difficulties and the complexity of the phase diagram are the reasons why in earlier publications even two separated phases in this compositional region were described. [3] First observed at the end of the 19th century as ab y-product during the reduction of boron oxide with carbon or magnesium (in carbon vessels), [4,5] boron carbide has continued to attract the attention of researchers and engineers for decades owing to its mechanical and thermal properties.The Vickers hardness and fracture toughness approaching the properties of diamond are the reason for the nickname "black diamond" and for application as lightweight protection. [6] Furthermore,boron carbide shows good properties against neutrons,s tability to extreme temperatures,i onizing radiation and most chemicals,a ll combined with al ow density.C onsequently,m ultiple applications of materials based on this substance were implemented since the middle of the 20th century.The fascination for this material is still so strong that it has even been supposed to be ah ightemperature superconductor. [7] Later, the thermoelectric properties of boron carbide came into the focus of researchers owing to the demand for efficient thermoelectric materials for high-temperature applications, [8][9][10][11][12][13] including the manufacturing of thermoelectric modules with boron carbide as the ptype material. [14] To understand the intrinsic reasons for the good thermoelectric performance,c entimeter-sized single crystals of this material were grown utilizing floating-zone technology. [15] In agreement with earlier results,t hese crystals show apositive Seebeck coefficient, that is,p-type semiconducting behavior (Supporting Information, Figure S1, top). Another group of boron cage compounds,the rare-earth borocarbonitrides RB 15.5 CN,R B 22 C 2 N, and Y 1Àx B 28.5 C 4 ,w as suggested as an-type boride-based counterpart to boron carbide. [16] Durin...

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Configurational order-disorder induced metal-nonmetal transition inB13C2studied with first-principles superatom-special quasirandom structure method

Cited by 22 publications

References 53 publications

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 ternary B-As-P system

Thermodynamic stability and properties of boron subnitrides from first principles

Local Atomic Arrangements and Band Structure of Boron Carbide

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