Structural, mechanical and thermodynamic properties study on Mg–Y alloys from first-principles calculations

2020 ◽  
Vol 34 (25) ◽  
pp. 2050220
Author(s):  
Yingying Chen ◽  
Xilong Dou ◽  
Wenjie Zhu ◽  
Gang Jiang ◽  
Aijie Mao
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
Crystal Structure Analysis ◽  
First Principles Calculations ◽  
Phonon Spectra ◽  
Volume Entropy ◽  
Ductile Behavior ◽  
Searching Method

The structures with different compositions of the binary Mg–Y alloys have been predicted by first-principles calculations combined with an unbiased Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) structure searching method. The two already known stoichiometries alloys of Mg1Y1 with Pm-[Formula: see text] symmetry and Mg3Y1 with Fm-[Formula: see text] are confirmed, and a new stoichiometry alloy of Mg1Y3 with [Formula: see text] symmetry is proposed. The dynamical and mechanical stabilities for the three alloys at different pressures are investigated by phonon spectra and mechanical stability criteria, respectively. Subsequently, the bulk modulus, shear modulus, Young’s modulus, the brittleness/ductile behavior, the elastic anisotropy as well as Vickers hardness for the three alloys at 0 GPa are discussed in detail. The results show that the Mg1Y1, Mg3Y1 and Mg1Y3 alloys improve the hardness and stiffness compared with pure Mg, and Mg1Y3 alloy is of the best ductility in the three alloys. Meanwhile, the three alloys exhibit anisotropic. Moreover, the thermodynamic properties, such as Debye temperature, heat capacity at constant volume, entropy and Helmholtz free energy for the three stable alloys, are predicted and discussed.

Pressure effects on mechanical and electronic properties of metallic C14 by first-principles calculation

2019 ◽  
Vol 33 (18) ◽  
pp. 1950193
Author(s):  
Yingjiao Zhou ◽  
Qun Wei ◽  
Bing Wei ◽  
Ruike Yang ◽  
Ke Cheng ◽  
...  
Keyword(s):  
High Pressure ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Pressure Range ◽  
Phonon Dispersion ◽  
Elastic Anisotropy ◽  
Acoustic Velocity ◽  
Pressure Effects ◽  
First Principles Calculation ◽  
First Principles Calculations

The elastic constants and phonon dispersion of metallic C[Formula: see text] are calculated by first-principles calculations. The results show that the metallic C[Formula: see text] is mechanically and dynamically stable under high pressure. The variations of G/B ratio, Poisson’s ratio, elastic anisotropy, acoustic velocity and Debye temperature at the pressure range from 0 GPa to 100 GPa are analyzed. The results reveal that by adjusting the pressures the elastic anisotropy and thermodynamic properties could be improved for better applicability.

scholarly journals Phase Stability, Elastic Modulus and Elastic Anisotropy of X Doped (X = Zn, Zr and Ag) Al3Li: Insight from First-Principles Calculations

Crystals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 7
Author(s):  
Jinzhong Tian ◽  
Yuhong Zhao ◽  
Shengjie Ma ◽  
Hua Hou
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
First Principles Calculations ◽  
Stability Criteria ◽  
Longitudinal Sound Velocity ◽  
Positive Effect ◽  
Shear Planes

In present work, the effects of alloying elements X (X = Zn, Zr and Ag) doping on the phase stability, elastic properties, anisotropy and Debye temperature of Al3Li were studied by the first-principles method. Results showed that pure and doped Al3Li can exist and be stable at 0 K. Zn and Ag elements preferentially occupy the Al sites and Zr elements tend to occupy the Li sites. All the Cij obey the mechanical stability criteria, indicating the mechanical stability of these compounds. The overall anisotropy decreases in the following order: Al23Li8Ag > Al3Li > Al23Li8Zn > Al24Li7Zr, which shows that the addition of Zn and Zr has a positive effect on reducing the anisotropy of Al3Li. The shear anisotropic factors for Zn and Zr doped Al3Li are very close to one, meaning that elastic moduli do not strongly depend on different shear planes. For pure and doped Al3Li phase, the transverse sound velocities νt1 and νt2 among the three directions are smaller than the longitudinal sound velocity νl. Moreover, only the addition of Zn is beneficial to increasing the ΘD of Al3Li among the three elements.

First-principles study of phase stability, elastic and thermodynamic properties of AlCrFeNi medium-entropy alloys

2020 ◽  
Vol 34 (25) ◽  
pp. 2050218
Author(s):  
Zhiqin Wen ◽  
Zhengguang Zou ◽  
Shuchao Zhang ◽  
Yuhong Zhao
Keyword(s):  
Thermodynamic Properties ◽  
Phase Stability ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Elastic Stiffness ◽  
Face Centered Cubic ◽  
Volume Deformation ◽  
Random Structures ◽  
Face Centered ◽  
Ductile Behavior

We have applied the first-principles method to predict the phase stability, elastic and thermodynamic properties of ternary (AlCrFe, AlCrNi, CrFeNi and AlFeNi) and quaternary (AlCrFeNi) medium-entropy alloys (MEAs). Both body-centered cubic (BCC) and face-centered cubic (FCC) disordered structures are described using the special quasi-random structures (SQSs) technique. AlCrFe, AlCrNi and AlCrFeNi are favorable in single BCC structures, while CrFeNi is likely to form a single FCC structure. Addition of Ni help stabilizes AlCrFeNi quaternary MEAs. Al and Cr addition are in favor of the formation of BCC AlCrFeNi. Addition of Al, Cr and Ni reduce the resistance to volume deformation for quaternary AlCrFeNi due to the effect of the average number of [Formula: see text]-electrons. The ternary MEAs have better resistance to shear deformation and elastic stiffness than quaternary AlCrFeNi. In addition, all the considered MEAs embody elastic anisotropy and AlCrFeNi are predicted to be ductile behavior. Finally, volumetric thermal expansion coefficient, constant volume heat capacity, vibrational and electronic entropy, and Helmholtz free energies of stable BCC AlCrFeNi, BCC AlCrFe, BCC AlCrNi and FCC CrFeNi are calculated using the Debye–Grüneisen model in temperature ranging from 0 to 1200 K to elucidate the relationships between thermodynamic parameters and temperature.

Structural, elastic and electronic properties of new superhard orthorhombic C28

2019 ◽  
Vol 33 (20) ◽  
pp. 1950227
Author(s):  
Rui Zhang ◽  
Qun Wei ◽  
Bing Wei ◽  
Ruike Yang ◽  
Ke Cheng ◽  
...  
Keyword(s):  
Band Structure ◽  
Electronic Properties ◽  
Vickers Hardness ◽  
First Principles ◽  
Superhard Material ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
First Principles Calculations ◽  
Stability Criteria ◽  
Imaginary Frequency

The structural, mechanical and electronic properties of recently reported superhard material C[Formula: see text] are studied by first-principles calculations. The unit cell of C[Formula: see text] is composed of 28 carbon atoms and all sp3 hybridized bonds. From 0 GPa to 100 GPa, C[Formula: see text] satisfies the mechanical stability criteria and the phonon spectrum of C[Formula: see text] has no imaginary frequency, which means that C[Formula: see text] is mechanically and dynamically stable. The results of hardness calculated show that C[Formula: see text] is a potential superhard material with the Vickers hardness of 84.0 GPa. By analyzing the elastic anisotropy, we found that elastic anisotropy of C[Formula: see text] increases with pressure. The calculations of band structure demonstrates that C[Formula: see text] is an indirect bandgap semiconductor with the gap of 4.406 eV. These analyses demonstrate C[Formula: see text] is a superhard semiconductor material.

Physical properties of osmium dinitride with fluorite, pyrite, marcasite, and monoclinic structures under high pressure: First-principles study

2015 ◽  
Vol 93 (4) ◽  
pp. 424-433 ◽  
Author(s):  
Ni-Na Ge ◽  
Yong-Kai Wei ◽  
Jia-Jin Tan ◽  
Guang-Fu Ji ◽  
Yan Cheng
Keyword(s):  
Phase Transition ◽  
Thermodynamic Properties ◽  
Sound Velocity ◽  
First Principles ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
Fluorite Structure ◽  
Mechanical Anisotropy ◽  
Total Density ◽  
Structure Phase Transition

The structure, phase transition, elastic, and thermodynamic properties of OsN2 have been studied via first-principles calculations. It is shown that the CoSb2 structure is more stable than other structures. By the calculated H-P relations at 0 K, we found that the phase transition of OsN2 from CoSb2 structure to marcasite structure (ε → δ) occurs at 16.8 GPa, while the phase transition pressure between pyrite structure and fluorite structure (γ → α) is 80 GPa. The results of obtained phase transitions are also confirmed by bond length, sound velocity, and thermal expansion coefficient under different pressures. The pressure dependences of the elastic constants, mechanical stability, and mechanical anisotropy of four structures of OsN2 have been investigated by finding that the fluorite (pyrite and marcasite) structure OsN2 is mechanically stable under hydrostatic pressure (up to 60 GPa). However, the monoclinic structure is mechanically unstable under pressure from 0 to 60 Gpa. The calculated elastic anisotropic factors show that OsN2 possesses high elastic anisotropy under pressure. Moreover, the calculations on total density of states show that OsN2 of different structures has a metallic character, in agreement with previous theoretical results. The thermodynamic properties and sound velocity under diverse pressures of OsN2 of the four structures have been also investigated successfully.

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