Anisotropic phonon thermal transport in two-dimensional layered materials

Highly Anisotropic to Isotropic Nature and Ultralow Out-of-Plane Lattice Thermal Conductivity of Layered PbClF-Type Materials

“…The layered materials are bonded through strong covalent/ionic bonds in the in-plane direction and coupled by weak van der Waals (vdW)/strong electrostatic interactions in the out-of-plane direction, i.e., bonding heterogeneity, thus resulting in a weak/strong structural anisotropy. , Therefore, through bonding heterogeneity, these layered materials provide an avenue for tailoring the phonon transport properties. Investigation of iso-structural layered materials with varying average atomic mass is intriguing because they allow us to study structure–property correlations by exploring the interplay between bonding heterogeneity and atomic mass and also their implications on lattice dynamics, thereby fine-tuning the phonon transport properties. , One of the most important phonon transport property is the lattice thermal conductivity ( κ l = 1 3 c v v g 2 τ , where c v is the specific heat at a constant volume and v g and τ are the phonon group velocity and lifetime, respectively). Exploring mechanisms to achieve low κ l is essential for discovering functional materials through chemical intuition in layered materials with low/heavy atomic mass and a large axial ratio ( c / a > 2) to fine-tune the chemical bonding and thereby phonon group velocities and scattering rates/lifetimes.…”

“…Investigation of iso-structural layered materials with varying average atomic mass is intriguing because they allow us to study structure−property correlations by exploring the interplay between bonding heterogeneity and atomic mass and also their implications on lattice dynamics, thereby fine-tuning the phonon transport properties. 1,2 One of the most important phonon transport property is the lattice thermal conductivity (…”

“…Discovery and design of functional quasi two-dimensional (2D) layered materials with extremely low or high lattice thermal conductivity (κ l ) are crucial for thermal energy management applications. , Ultralow κ l materials find potential applications in thermoelectrics, , thermal insulation, , thermal storage, , and thermal barrier coatings, − while high κ l materials find applications in power electronics and solid state lighting. , A plethora of mechanisms ,− including rattling, , strong quartic anharmonicity, , bonding heterogeneity, and various chemical bonding principles were proposed to achieve low κ l . Among them, bonding heterogeneity is an essential mechanism, and it is an intrinsic property of layered materials.…”

“…Among them, bonding heterogeneity is an essential mechanism, and it is an intrinsic property of layered materials. The layered materials are bonded through strong covalent/ionic bonds in the in-plane direction and coupled by weak van der Waals (vdW)/strong electrostatic interactions in the out-of-plane direction, i.e., bonding heterogeneity, thus resulting in a weak/strong structural anisotropy. , Therefore, through bonding heterogeneity, these layered materials provide an avenue for tailoring the phonon transport properties. Investigation of iso-structural layered materials with varying average atomic mass is intriguing because they allow us to study structure–property correlations by exploring the interplay between bonding heterogeneity and atomic mass and also their implications on lattice dynamics, thereby fine-tuning the phonon transport properties. , One of the most important phonon transport property is the lattice thermal conductivity ( , where c v is the specific heat at a constant volume and v g and τ are the phonon group velocity and lifetime, respectively).…”

Evaluating In-Plane Thermal Expansion of Two-Dimensional Layered Materials via Effective Descriptors

“…A great deal of attention has been devoted to two-dimensional layered materials owing to their extraordinary electronic, − optical, , magnetic, , thermal, − and mechanical properties. − For example, the transition-metal dichalcogenide MoS 2 shows potential applications in transistors, − photodetectors, − field emitters, , memory, ,, and supercapacitors. , Two-dimensional layered material-based devices offer remarkable improvements in performance. However, thermal management issues restrict the practical application of these devices. − Fine-tailoring lattice thermal expansion is crucial for engineering applications, especially aerospace and precision instruments. , The thermal expansion behavior without being properly controlled can affect the performance and accuracy of the device . Seriously, larger residual stress and distortion can be introduced during the thermal expansion process, degrade device performance, and even accelerate device failure. − …”