Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (2): 253-260.doi: 10.3866/PKU.WHXB201412242

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

First-Principles Study into the Effect of Substitutional Al Alloying on the Mechanical Properties and Electronic Structure of D88-Ti5Si3

HUANG Hao-Jie, XU Jiang   

  1. School of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China
  • Received:2014-10-30 Revised:2014-12-24 Published:2015-01-26
  • Contact: XU Jiang E-mail:xujiang73@nuaa.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51374130) and Aeronautical Science Foundation of China (2013ZE52058).

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Abstract:

The influence of the substitution of Al for Si on the structural stability and mechanical properties of D88-Ti5Si3 was determined using first-principles pseudopotential plane-wave methods based on density functional theory. Several parameters including formation enthalpies ((ΔHf), cohesive energies (ΔEcoh), bulk modulus (B), shear modulus (G),Poisson's ratio (ν), Cauchy's pressure (C12-C66,C13-C44), metallicity (fm), and Peierls stress (τP-N) were calculated. To develop a better understanding of the effects of substitutional Al alloying on the toughness/brittleness of D88-Ti5Si3 from an electronic structure point of view the density of states, charge density differences and Mulliken population were determined. The results show that the intrinsic brittleness of D88-Ti5Si3 comes from strong covalent bonding between Ti6g and Si6g.When one or two Ti atoms occupy Si sites in the D88- Ti5Si3 crystal the intensity of covalent bonding between Ti6g and Si6g is reduced and the metallicity increases. This is accompanied by the presence of low intensity Al6g―Si6g, Ti6g―Al6g, and Ti4d―Al6g bonds. However, when three Ti atoms occupy Si sites in the D88-Ti5Si3 crystal the Al6g―Si6g bonds disappear and the intensity of covalent bonding between Ti6g and Si6g increases leading to an increase in brittleness.

Key words: First-principles, Titanium-silicon compound, Chemical bond, Ductile/brittle behavior, Electronic structure