Structural prediction of ultrahard semi-titanium boride (Ti2B) using the frozen-phonon method

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Titanium boride (Ti2B) has been long assumed to possess an Al2Cu-type structure.
• Understanding the precise crystal structure is crucial for predicting material properties.

Purpose of the Study:

• To investigate the dynamical stability, crystal structure, and mechanical properties of titanium boride (Ti2B).
• To identify the most stable crystal structure and its associated properties.

Main Methods:

• Utilized first-principles calculations with the pseudopotential plane-wave method.
• Employed the frozen-phonon method to determine structural stability.
• Calculated phonon dispersion and elastic constants.

Main Results:

• Identified soft transverse acoustic phonon modes in the previously assumed structure.
• Uncovered a more energetically stable tetragonal I4/m structure for Ti2B.
• Confirmed dynamical and mechanical stability of the I4/m structure at ambient pressure.
• Calculated high elastic constants, modulus, and ideal strength, indicating outstanding mechanical properties.

Conclusions:

• The tetragonal I4/m structure is the stable phase of Ti2B.
• Ti2B exhibits excellent mechanical properties, making it a promising material for various applications.
• The findings correct previous assumptions about Ti2B's crystal structure.