Remarkable decrease in lattice thermal conductivity of transition metals borides TiB₂by dimensional reduction.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Two-dimensional transition metal borides, such as titanium borides (TiB), exhibit promising magnetic and electronic properties for metal-ion batteries and energy storage.
• Effective thermal management is critical for ensuring the safety and stability of these energy storage devices.

Purpose of the Study:

• To investigate the lattice dynamics and thermal transport properties of bulk and two-dimensional (2D) titanium borides (TiB).
• To understand the impact of dimension reduction on thermal conductivity and compare it with other 2D materials.

Main Methods:

• Utilized density functional theory (DFT) calculations.
• Employed the phonon Boltzmann transport equation to analyze thermal properties.
• Investigated Poisson's ratio, Debye temperature, phonon group velocity, and anharmonic effects.

Main Results:

• Poisson's ratio transitions from positive in bulk TiB$_{2}$ to negative in monolayer TiB$_{2}$.
• Dimension reduction leads to a decrease in room-temperature in-plane lattice thermal conductivity, contrary to MoS$_{2}$, MoSe$_{2}$, WSe$_{2}$, and SnSe.
• Monolayer TiB$_{2}$ exhibits one-sixth the thermal conductivity of bulk TiB$_{2}$ due to higher Debye temperature and stronger bonding stiffness.
• Monolayer Ti$_{2}$B$_{2}$ shows double the thermal conductivity of monolayer TiB$_{2}$, attributed to symmetry-induced phonon selection rules.

Conclusions:

• The thermal transport behavior of 2D TiB materials differs significantly from other established 2D counterparts.
• Reduced dimensionality in TiB materials leads to decreased thermal conductivity, impacting their suitability for thermal management in energy storage.
• Understanding these unique thermal properties is essential for designing stable and safe energy storage devices based on 2D TiB.