Computational materials discovery: the case of the W-B system

Area of Science:

• Materials Science
• Computational Materials Science
• Solid State Chemistry

Background:

• The tungsten-boron (W-B) system has a complex and historically inconsistent experimental record.
• Understanding the phase diagram and properties of W-B compounds is crucial for developing advanced materials.

Purpose of the Study:

• To theoretically investigate the compositions, structures, and mechanical properties of the W-B system.
• To predict new stable and metastable tungsten boride phases.
• To systematically derive elastic properties and Vickers hardness for known and predicted compounds.

Main Methods:

• Variable-compositional evolutionary algorithms were employed.
• First-principles calculations were utilized for theoretical investigations.
• Mechanical properties, including elastic moduli and Vickers hardness, were systematically derived.

Main Results:

• Four known compounds (W2B, WB, WB2, WB3) were confirmed, and three new compounds (W8B7, W2B3, WB4) were predicted.
• hP6-WB2 shows ultra-incompressibility (C33 = 953 GPa).
• hP16-WB3 exhibits high hardness (36.9 GPa), approaching the superhard threshold.
• oC8-WB demonstrates a high bulk modulus (approx. 350 GPa).
• The stable W8B7 compound features infinite zigzag B chains and a hardness of 19.6 GPa.
• Anisotropic properties (Young's modulus E, torsion shear modulus G(t)) were derived for oC8-WB and hP16-WB3.
• Previous experimental attribution of hP20-WB4 was clarified as defect-containing hP16-WB3.

Conclusions:

• The study successfully predicted new stable and metastable tungsten borides.
• WB3 and WB2 show promising properties for potential superhard and incompressible material applications, respectively.
• The findings clarify historical inconsistencies in the W-B system and provide a reliable database for future research and development.