Yifang Ouyang

First principle study of AlX (X=3d,4d,5d elements and Lu) dimer

The ground state equilibrium bond length, harmonic vibrational frequency, and dissociation energy of AlX (X=3d,4d,5d elements and Lu) dimers are investigated by density functional method B3LYP. The present results are in good agreement with the available experimental and other theoretical values except the dissociation energy of AlCr. The present calculations show that the late transition metal can combine strongly with aluminum compared with the former transition metal. The present calculation also indicates that it is more reasonable to replace La with Lu in the Periodic Table and that the bonding strengths of zinc, cadmium, and mercury with aluminum are very weak.

First-principles calculations of the thermodynamic and elastic properties of the L12-based Al3RE (RE = Sc, Y, La–Lu)

Abstract First-principles calculations of the total energy and elastic properties of the L12-based Al3RE (RE = Sc, Y, Lanthanide) at T = 0 K are performed by using the projector augmented-wave method within the generalized gradient approximation. The lattice constants, formation enthalpies, elastic constants and bulk modulus of the L12-based Al3RE are obtained. Youngs modulus, shear modulus and Poissons ratios are also estimated in the present work. By using the Debye – Grüneisen model, the Debye temperatures, Grüneisen constants and the sound velocity are obtained for the L12-based Al3RE. All the calculated results are in good agreement with experimental values and other theoretical calculations available.

First-principles calculations of elastic constants of DO3-Mg3 RE (RE = Sc, Y, La, Ce, Lu)

The elastic constants of DO3-Mg3 RE (RE = Sc, Y, La, Ce and Lu) have been calculated at T = 0?K by applying the projector augmented wave (PAW) method within the generalized gradient approximation (GGA). The polycrystalline shear modulus, Youngs modulus, Poissons ratio and the anisotropic ratio of DO3-Mg3 RE are also estimated. The density of states and bonding charge densities of DO3-Mg3 Ce and DO3-Mg3 Er are calculated to understand the bonding characteristics of Mg3 RE. The calculated results indicate that the rare earth (RE) additions can improve the elastic modulus of Mg alloys. The predicted elastic constants of DO3-Mg3 RE provide helpful guidance for the design of novel Mg alloys.

The elastic constants for Fe3AlX (X=B, C and N) with anti-perovskite structure

The total energy and bulk properties of Fe3AlX (X=B, C and N) with anti-perovskite structure at T=0 K were calculated by using the projector augmented-wave (PAW) approach within generalized gradient approximation (GGA) and local density approximation (LDA). The lattice constant, bulk modulus and its pressure derivative, elastic constants, shear modulus, Poissons ratio and Debye temperature both in paramagnetic and ferromagnetic states for Fe3AlX have been calculated. The calculations indicate that the ground states of Fe3AlB and Fe3AlC are ferromagnetic, while for Fe3AlN its ground state is paramagnetic. The calculated total energy within LDA is lower than that within GGA. The calculated lattice constant of Fe3AlC within GGA is in good agreement with experimental value, and this indicates that the calculations from GGA are more accurate than those from LDA. The calculated elastic constants and bulk moduli agree with other theoretical results available. The average magnetic moments of Fe in Fe3AlX (X=B, C and N) are 1.483, 1.103 and 0.0 μB (GGA), or 1.300, 0.401 and 0.0 μB (LDA), respectively.

First-principles generated mechanical property database for multi-component al alloys: Focusing on Al-rich corner

Systematic first-principles calculations of the single crystal elastic stiffness constants (cijs) and the polycrystalline aggregates including bulk modulus (B), shear modulus (G), Youngs modulus (E) have been performed for series binary and ternary Al compounds at 0 K. In addition, the temperature-dependent elastic properties for some technologically important phases are calculated. The cijs are calculated by means of an efficient strain-stress method. Phonon density of states or Debye model is employed to calculate the linear thermal expansion, which is then used to calculate the temperature dependence of elastic properties. The calculated temperature-dependent elastic properties are compiled in the format of CALPHAD (CALculation of PHAse Diagram) type formula. The presently computed elastic properties for Al compounds are needed for simulation of microstructure evolution of commercial Al alloys during series of processing route.

Elastic constants and thermophysical properties of Al–Mg–Si alloys from first-principles calculations

Abstract The lattice constants and elastic constants for Al–Mg–Si alloys have been calculated by using first-principles total energy calculations within the generalized gradient approximation. The calculated results are in good agreement with available experimental and theoretical results. The polycrystalline shear modulus, Youngs modulus and Poissons ratio are also estimated from the calculated single crystalline elastic constants. The Youngs modulus and shear modulus increase following the precipitation sequence in Al–Mg–Si. The Debye sound velocity, Debye temperature, Grüneisen constant, heat capacity and linear coefficients of thermal expansion are predicted for the considered Al–Mg–Si alloys based on the Debye–Grüneisen model. The calculated values of Mg2Si agree well with the previous experimental and theoretical results.