The helium bubble structure and growth modes near dislocations in titanium are studied using the molecular dynamics method. A helium crystal with an HCP structure in titanium is found to have a lattice constant of 1.9...The helium bubble structure and growth modes near dislocations in titanium are studied using the molecular dynamics method. A helium crystal with an HCP structure in titanium is found to have a lattice constant of 1.977 A? at 0 K. On either side of the slip plane, helium bubbles form in the(001) plane, but they are in different growth modes. On the side of the slip plane with full atomic layers, helium bubbles grow toward the slip plane and easily cross the slip plane. In the growth process, the position of the top surface of the helium bubble remains almost unchanged. On the other side of the slip plane,the helium bubble grows initially toward the dislocation core, but it is difficult to cross the slip plane, which results in growth in the opposite direction upon reaching the slip plane.展开更多
In this work,the impacts of pressure on the structural,mechanical,thermodynamic and electronic properties of typical Pt_(3)M(M=Al,Co,Hf,Sc,Y,Zr)compounds were investigated systematically by the firstprinciples density...In this work,the impacts of pressure on the structural,mechanical,thermodynamic and electronic properties of typical Pt_(3)M(M=Al,Co,Hf,Sc,Y,Zr)compounds were investigated systematically by the firstprinciples density function theory calculations.The calculated lattice parameters,volume and elastic constants of Pt_(3)M compounds are in good agreement with available experimental and calculation values.With the increase in pressure,the lattice parameters and volume of Pt_(3)M compounds decrease,while the elastic constants,bulk modulus,shear modulus and Young’s modulus increase.The variations in Pugh’s ratio and Poisson’s ratio indicate that these Pt_(3)M compounds are mechanically stable and ductile.The mechanical anisotropy of these Pt_(3)M compounds is enhanced by rising pressure.Thermodynamic analysis indicates that sound velocity and Debye temperature increase with the increase in stress.The charge distribution does not change obviously,implying that no phase transition occurs in the range of 0-100 GPa.展开更多
High-entropy carbide ceramics (HECs) have drawn increasing attention as their excellent mechanical and thermal properties. In this work, the crystal stability,mechanical behavior, electronic and thermodynamic properti...High-entropy carbide ceramics (HECs) have drawn increasing attention as their excellent mechanical and thermal properties. In this work, the crystal stability,mechanical behavior, electronic and thermodynamic properties of (TiZrNbTa)C HEC are investigated by the first-principles calculations. Obtained results reveal that the disordered transition-metal (TM) atoms result in serious local lattice distortion within the crystal. The lattice distortion plays a key role for the structural stabilization,mechanical anisotropy and thermodynamic behaviors of(TiZrNbTa)C. Increasing pressure leads to decrease the lattice parameter, volume and brittleness, meanwhile increase the elastic constants, elastic moduli, mechanical anisotropy, sound velocity, and Debye temperature. It is also discovered that charge delocalization occurs with the increase in pressure. The mechanical stability and anisotropy of (TiZrNbTa)C are attributed primarily to TM-C bonding.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11505120)the Project of Innovative Talents of North China University of Water Resources and Electric Power,China(Grant No.70483)
文摘The helium bubble structure and growth modes near dislocations in titanium are studied using the molecular dynamics method. A helium crystal with an HCP structure in titanium is found to have a lattice constant of 1.977 A? at 0 K. On either side of the slip plane, helium bubbles form in the(001) plane, but they are in different growth modes. On the side of the slip plane with full atomic layers, helium bubbles grow toward the slip plane and easily cross the slip plane. In the growth process, the position of the top surface of the helium bubble remains almost unchanged. On the other side of the slip plane,the helium bubble grows initially toward the dislocation core, but it is difficult to cross the slip plane, which results in growth in the opposite direction upon reaching the slip plane.
基金financially supported by the National Natural Science Foundation of China(No.51801179)Yunnan Science and Technology Projects(Nos.2019ZE001-1,2018ZE001,2018ZE021 and 2018IC058)Yunnan Applied Basic Research Projects(Nos.2018FB083 and 2018FD011)。
文摘In this work,the impacts of pressure on the structural,mechanical,thermodynamic and electronic properties of typical Pt_(3)M(M=Al,Co,Hf,Sc,Y,Zr)compounds were investigated systematically by the firstprinciples density function theory calculations.The calculated lattice parameters,volume and elastic constants of Pt_(3)M compounds are in good agreement with available experimental and calculation values.With the increase in pressure,the lattice parameters and volume of Pt_(3)M compounds decrease,while the elastic constants,bulk modulus,shear modulus and Young’s modulus increase.The variations in Pugh’s ratio and Poisson’s ratio indicate that these Pt_(3)M compounds are mechanically stable and ductile.The mechanical anisotropy of these Pt_(3)M compounds is enhanced by rising pressure.Thermodynamic analysis indicates that sound velocity and Debye temperature increase with the increase in stress.The charge distribution does not change obviously,implying that no phase transition occurs in the range of 0-100 GPa.
基金financially supported by the National Natural Science Foundation of China (No. 51801179)Yunnan Science and Technology Projects (Nos. 2018ZE001, 2019ZE001-1, 202002AB080001-6, 2018IC058, 2018FB083 and 2018FD011)the support from the Yunnan Provincial High-level Talents Introduction Projects。
文摘High-entropy carbide ceramics (HECs) have drawn increasing attention as their excellent mechanical and thermal properties. In this work, the crystal stability,mechanical behavior, electronic and thermodynamic properties of (TiZrNbTa)C HEC are investigated by the first-principles calculations. Obtained results reveal that the disordered transition-metal (TM) atoms result in serious local lattice distortion within the crystal. The lattice distortion plays a key role for the structural stabilization,mechanical anisotropy and thermodynamic behaviors of(TiZrNbTa)C. Increasing pressure leads to decrease the lattice parameter, volume and brittleness, meanwhile increase the elastic constants, elastic moduli, mechanical anisotropy, sound velocity, and Debye temperature. It is also discovered that charge delocalization occurs with the increase in pressure. The mechanical stability and anisotropy of (TiZrNbTa)C are attributed primarily to TM-C bonding.