Theoretical Investigations on the Structural, Electronic, Mechanical, and Thermal Properties of MP₂O₇ (M = Ti,Hf)

Abstract

A systematical ab initio analysis on MP 2 O 7 (M = Ti, Hf) is presented in this work. Density functional theory (DFT) computations were performed for the electronic, mechanical, and thermal properties of MP 2 O 7 . Heterogeneous bonding nature of MP 2 O 7 was revealed by examining the structural and electronic properties, M-O bonds were weaker than P-O bonds. The elastic constants and polycrystalline mechanical properties of MP 2 O 7 were reported. Based on the low shear-modulus-tobulk-modulus ratios and positive Cauchy pressure, MP 2 O 7 ceramics were predicted to be "quasi-ductile". In addition, the minimum thermal conductivities were estimated to be 1.52 and 0.99 WÁm -1 ÁK -1 for TiP 2 O 7 and HfP 2 O 7 , respectively. The ultra-low thermal conductivities were contributed to the lattice phonon scattering due to the heterogeneous bonding nature. Our theoretical results emphasize the importance of weak M-O bonds in the determination of mechanical and thermal properties of MP 2 O 7 .

Mechanical and Thermal Properties of Yb2SiO5: A Promising Material for T/EBCs Applications

“…As most of the recently recognized promising materials for T/EBCs applications such as β‐Yb 2 Si 2 O 7 , γ‐Y 2 Si 2 O 7 , Y 2 SiO 5 , Y 4 Al 2 O 9 , Yb 3 Al 5 O 12 , YbAlO 3 , MP 2 O 7 (M=Ti, Zr, Hf), AlPO 4 , and MSiO 4 (M=Zr, Hf), Yb 2 SiO 5 is characterized by low shear deformation resistance (low shear modulus G) and low Pugh's ratio (shear to bulk modulus ratio, G/B). Using Pugh's ratio as a criterion, Yb 2 SiO 5 was predicted to be a damage‐tolerant ceramic .…”

Electronic structure, anisotropic elastic and thermal properties of the η phase Fe 6 W 6 C

“…In this paper, the anisotropy of torsion shear modulus for Fe 6 W 6 C (G T ) is discussed to solve the problem. The directional dependence of torsion shear modulus and Young's modulus is given by [18,19]: The anisotropy of the minimum thermal conductivity for Fe 6 W 6 C is now addressed based on Cahill's model and Clarke's model. Both models can give the lower limit of the thermal conductivity of a crystal.…”

Suppressing the phase transition of ZrP 2O 7 by defect and entropy regulation for high-temperature wave-transparent material application

“…For crystalline materials with defects, there is a negative correlation between thermal conductivity and phonon scattering coefficient. The phonon scattering coefficient is dominated by defects [47,48]:…”