Elastic Properties of Orthorhombic YBa2Cu3O7 under Pressure

Abstract

The pressure dependence of the lattice and elastic constants of the orthorhombic YBa 2 Cu 3 O 7 are firstly investigated using the first principles calculations based on the density functional theory. The calculated lattice parameters at 0 GPa are in agreement with the available experimental data. By the elastic stability criteria under isotropic pressure, it is predicted that YBa 2 Cu 3 O 7 with and orthorhombic structure is mechanically stable under pressure up to 100 GPa. On the basis of the elastic constants, Pugh’s modulus ratio, Poisson’s ratio, elastic anisotropy, Debye temperature, and the minimum thermal conductivity of YBa 2 Cu 3 O 7 under pressure up to 100 GPa are further investigated. It is found that its ductility, Debye temperature, and minimum thermal conductivity increase with pressure.

Effect of pressure on mechanical and optical properties of ThO2 and PuO2

“…The bulk modulus represents the resistance to isotropic hydrostatic pressure against the deformation in volume and is associated with the bond length of the crystal. 43,53,55 As we have reported in our previous work, 29 the bond length of Pu-O is shorter than Th-O; therefore, PuO 2 has stronger bonding and a higher value of B than ThO 2 . ThO 2 shows a higher value of G and E than PuO 2 in a cubic structure.…”

“…The positive value of elastic constants shows the mechanical stability of these oxides. The elastic stiffness constants C ij , ∀ i , j = 1, 2, 3 are associated with resistance to linear compression, whereas C ij , ∀ i , j = 4, 5, 6 represent elasticity in shape 43,54 . For the cubic structure, PuO 2 indicates higher resistance to linear compression but lower shear resistance as compared to ThO 2 , as C 11 and C 12 are higher for PuO 2 but C 44 is lower than ThO 2 .…”

“…ThO 2 shows a higher value of G and E than PuO 2 in a cubic structure. The shear modulus ( G ) is an elastic response to applied stress against shape change and is associated with the bond‐angle of the material 43,53,55 . A larger value of shear modulus indicates more notable directional bonding between atoms.…”

“…For orthorhombic systems, 43,44 $$$$\begin{equation*}\ {B}_V = \ \frac{1}{9}\left( {{C}_{11} + 2{C}_{12} + 2{C}_{13} + {C}_{22} + 2{C}_{23} + {C}_{33}} \right)\end{equation*}$$$$$$$$\begin{eqnarray*} {G}_V &=& \frac{1}{{15}}\left( {{C}_{11} - {C}_{12} - {C}_{13} + {C}_{22} - {C}_{23} + {C}_{33}}\right.\\ && \left. { + 3{C}_{44} + 3{C}_{55} + 3{C}_{66}} \right)\end{eqnarray*}$$$$$$$$\begin{e...$$…”

3D Porous Metallic Boron Carbide Crystal Structure with Excellent Ductility

“…Our work presents a novel ductile 3D porous crystal boron carbide with an equal atomic ratio of B and C. In General, Poisson's ratio has values in the range of −1.0 to 0.50, and 0.25 is a low limit for central force materials. [43] For 3D-B 6 C 6 , the computed value of v is larger than this limit (as shown in Table 2), indicating that central forces are predominated in the interatomic interactions of this porous structure.…”