First-Principles Study on Structural, Mechanical, Anisotropic, Electronic and Thermal Properties of III-Phosphides: <i>X</i>P (<i>X</i> = Al, Ga, or In) in the <i>P</i>6₄22 Phase

• Main Authors: Junjie Miao, Changchun Chai, Wei Zhang, Yanxing Song, Yintang Yang
• Format: Article
• Language: English
• Published: MDPI AG 2020-02-01
• Series: Materials
• Subjects: iii-phosphide; <i>p</i>6₄22 phase; density functional theory; mechanical properties; band-gap properties; thermal properties
• Online Access: https://www.mdpi.com/1996-1944/13/3/686
• ISSN: 1996-1944

The structural, mechanical, electronic, and thermal properties, as well as the stability and elastic anisotropy, of <i>X</i>P (<i>X</i> = Al, Ga, or In) in the <i>P</i>6₄22 phase were studied via density functional theory (DFT) in this work. <i>P</i>6₄22-<i>X</i>P (<i>X</i> = Al, Ga, or In) are dynamically and thermodynamically stable via phonon spectra and enthalpy. At 0 GPa, <i>P</i>6₄22-<i>X</i>P (<i>X</i> = Al, Ga, or In) are more rigid than <i>F</i><inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mn>4</mn> <mo>&#175;</mo> </mover> <mn>3</mn> </mrow> </semantics> </math> </inline-formula><i>m</i>-<i>X</i>P (<i>X</i> = Al, Ga, or In), of which <i>P</i>6₄22-<i>X</i>P (<i>X</i> = Al or Ga) are brittle and <i>P</i>6₄22-InP is ductile. In the same plane (except for (001)-plane), <i>P</i>6₄22-AlP and <i>P</i>6₄22-InP exhibit the smallest and the largest anisotropy, respectively, and <i>P</i>6₄22-<i>X</i>P (<i>X</i> = Al, Ga, or In) is isotropic in the (001)-plane. In addition, Al, Ga, In, and P bonds bring different electrical properties: <i>P</i>6₄22-InP exhibits a direct band gap (0.42 eV) with potential application for an infrared detector, whereas <i>P</i>6₄22-<i>X</i>P (<i>X</i> = Al or Ga) exhibit indirect band gap (1.55 eV and 0.86 eV). At high temperature (approaching the melting point), the theoretical minimum thermal conductivities of <i>P</i>6₄22-<i>X</i>P (<i>X</i> = Al, Ga, or In) are AlP (1.338 W∙m^&#8722;1∙K^&#8722;1) &gt; GaP (1.058 W∙m^&#8722;1∙K^&#8722;1) &gt; InP (0.669 W∙m^&#8722;1∙K^&#8722;1), and are larger than those of <i>F</i><inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mn>4</mn> <mo>&#175;</mo> </mover> <mn>3</mn> </mrow> </semantics> </math> </inline-formula><i>m</i>-<i>X</i>P (<i>X</i> = Al, Ga, or In). Thus, <i>P</i>6₄22-<i>X</i>P (<i>X</i> = Al, Ga, or In) have high potential application at high temperature.