Screening of 225 Double-Transition-Metal o-MXenes for Superior Thermoelectric Property at Room Temperature from First-Principles Electron and Phonon Calculations

Abstract

The high-throughput workflows are developed to efficiently and reliably predict the electrical and thermal conductivities of double-transition-metal o-MXenes. We conduct the calculations for 225 double-transition-metal o-MXenes with different transition-metal combinations, surface terminations (−H, −F, −O, and −OH), and structural types (“212” and “223”). For all investigated o-MXenes, their electrical conductivities are found to be in the range from 105 up to 107 S/m, indicating that o-MXenes are good electron conductors. With regard to the thermal conductivity, electron thermal conduction dominates the total thermal conductivity for surface functionalized o-MXenes. In the case of intrinsic o-MXenes, lattice thermal conductivity is comparable to that of electron thermal conduction. Surface terminations show great influence on both phonon and electron transport properties. It is revealed that O-termination tends to produce semiconducting o-MXenes, while the OH-termination effectively reduces the lattice thermal conductivity of o-MXenes. Dozens of o-MXenes are predicted to be potentially excellent thermoelectric materials for the first time and which are found to possess Seebeck coefficients higher than 100 μV/K and have ZT values larger than 0.5 at room temperature.

Fast access of the lattice thermal conductivity and phonon quasiparticle spectra of Mo2TiC2T2 (T = –O and –F) and Janus Mo2TiC2OF MXenes from machine learning potentials

“…The dominance of F atoms in the phonon spectrum of F-terminated MXenes at the lower frequency has been reported before. 84 The above results indicate that the inter-atomic bonding between F and Mo atoms is much weaker than Mo–O bonds.…”

“…It is also worth noting that the lattice thermal conductivities obtained for Mo 2 TiC 2 , Mo 2 TiC 2 O 2 and Mo 2 TiC 2 F 2 monolayers using the MTPs are also different to those reported in ref. 84 within the harmonic phonon calculations. Using the MTPs trained for atomic forces and total energies at finite temperatures can partly incorporate higher order anharmonic effects in the renormalized second order and third order inter-atomic force constants, leading to a more reliable description for phonon conduction than that of harmonic approximation.…”

“…The electron relaxation times of the investigated MXenes are obtained from our previous work. 84 The obtained electron thermal conductivities of MXenes are displayed in Fig. 11 in a temperature range from 200 K to 800 K. At 300 K, the predicted electron thermal conductivities of Mo 2 TiC 2 , Mo 2 TiC 2 O 2 , Mo 2 TiC 2 F 2 and Janus-Mo 2 TiC 2 OF monolayers are found to be 41.42 W m −1 K −1 , 0.90 W m −1 K −1 , 47.34 W m −1 K −1 , and 43.51 W m −1 K −1 , respectively.…”

“…The electron relaxation times of the investigated MXenes are obtained from our previous work. 84 The obtained electron thermal conductivities of MXenes are displayed in Fig. 11 dominance of the electron thermal conduction mechanism in the total thermal conductivity of Mo 2 TiC 2 F 2 and Janus-Mo 2 TiC 2 OF monolayers is clearly illustrated in Fig.…”

Exploring the large chemical space in search of thermodynamically stable and mechanically robust MXenes via machine learning

“…Similarly, Guha et al 19 investigated MXene transistors with low-resistive contacts and sequentially calculated electronic (such as the bandgap and in-plane static dielectric constant), structural, and thermodynamic properties using DFT. Other studies employing HTCS have successfully identified optimal MXenes by computing various properties, including mechanical properties such as in-plane stiffness, 20 thermoelectric properties such as Seebeck coefficients, 21 and magnetic properties such as ferroelectricity. 22 The ability to accurately identify and screen various properties of MXenes using computational methods is crucial in HTCS, which has made HTCS an invaluable method in MXene research.…”