scholarly journals Structural stability, hardness, fracture toughness and melting points of Ta1-xHfxC and Ta1-xZrxC ceramics from first-principles

2020 ◽  
Author(s):  
Shuoxin Zhang ◽  
Shiyu Liu ◽  
Dali Yan ◽  
Qian Yu ◽  
Haitao Ren ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Melting Point ◽  
Solid Solutions ◽  
First Principles ◽  
Formation Energy ◽  
Elastic Moduli ◽  
Melting Points ◽  
Virtual Crystal Approximation ◽  
Lattice Constants ◽  
The Stability

Abstract We systematic investigated the influence of substitution of Hf and Zr atoms for Ta atoms in TaC using first-principles supercell (SC) method and virtual crystal approximation (VCA) methods, including the impurity formation energy, lattice constant, volume, elastic constants, elastic moduli, melting points, fracture toughness and density of states of the Ta 1-x Hfx C and Ta1-x Zrx C ceramics in the whole range of content 0≤ x ≤1. Our calculated results show that the stability of Ta 1-x Hf x C and Ta 1-x Zrx C increases with the increase of Hf and Zr content, and Ta1-x Zrx C is more stable than Ta1-x Hfx C at the same content of Hf and Zr. The lattice constants and volumes dilate with the increase of Hf and Zr content. Furthermore, Ta1-x Hfx C and Ta1-x Zrx C carbides are mechanically stable and brittle. The bulk modulus of Ta1-x Hfx C and Ta1-x Zrx C decreases with the increasing content of Hf and Zr. Moreover, the hardness, fracture toughness, and melting point of Ta1-x Hf x C and Ta1-x Zrx C solid solutions have the peak. In particular, Ta0.8Hf0.2C has the highest hardness, largest fracture toughness and highest melting temperature.

The stability, fracture toughness and electronic structure at γ-Ni (101)/(Ti, Nb)C (110) interface: A first-principles investigation

2019 ◽  
Vol 496 ◽  
pp. 143742 ◽  
Author(s):  
Shuting Sun ◽  
Hanguang Fu ◽  
Shuangye Chen ◽  
Jiacai Kuang ◽  
Xuelong Ping ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Electronic Structure ◽  
First Principles ◽  
The Stability

scholarly journals An investigation of the dissociation pressures and melting points of the system Copper-cuprous oxide

1912 ◽  
Vol 87 (598) ◽  
pp. 524-534 ◽  
Keyword(s):  
Melting Point ◽  
Solid Solutions ◽  
Cuprous Oxide ◽  
Eutectic Temperature ◽  
Eutectic Point ◽  
Cooling Curve ◽  
Melting Points ◽  
Platinum Crucible ◽  
Dissociation Pressures

E. Heyn determined the melting points of mixtures of copper and cuprous oxide of compositions varying between 100 per cent. Cu and 88·24 per cent. Cu, 11·76 per cent. Cu 2 O. The results of his experiments are shown by the points marked + in fig. 1. These points fall on two curves intersecting at the eutectic point 1065° C., Cu 2 O 3·5 per cent., Cu 96·5 per cent. Heyn found that all his mixtures showed a halt in the cooling curve at this eutectic temperature, so that within the range of his experiments there is no evidence of the existence of solid solutions. C. N. Otin has lately published some experiments on the melting points of the system cuprous oxide-silica. He attempted to determine the melting point of cuprous oxide, but as some oxidation always took place in his experiments, and as he did not analyse the solid obtained (on account of having to remelt it to get it out of the platinum crucible), there is some doubt as to the actual composition of the substance of which he determined the melting point. The highest temperature at which he found a halt in the cooling curve was 1205° C.

First-Principles Study on Al or/and P Doped SiC Nanotubes

2012 ◽  
Vol 510 ◽  
pp. 747-752 ◽  
Author(s):  
Ai Qing Wu ◽  
Qing Gong Song ◽  
Li Yang
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Formation Energy ◽  
Electronic Devices ◽  
Structural Distortion ◽  
First Principles Study ◽  
Type Semiconductor ◽  
The Stability

The stability and electronic structures of Al or/and P doped single-walled SiC nanotubes (SWSiCNTs) are investigated by the first-principles theory. It is found that the ones with P atom located at Si site are most energetically favorable both for armchair and zigzag SWSiCNTs, which means that P atom is prone to substitute Si atom. In the same time, we found that the formation energy of Al substituting Si atom is lower than that of Al substituting C atom. The energetic disadvantages of P or Al atom located at C site in SWSiCNTs may be due to the obviously structural distortion in view of that the Al and P atoms are much bigger than C atom. The SWSiCNTs can be routinely modified ranging fromp-type semiconductor ton-type by Al and P substitution doping. These results are expected to give valuable information in building nanoscale electronic devices.

First-Principles Study of Formation and Properties of Fcc-NdOx in Nd-Fe-B Sintered Magnets

2010 ◽  
Vol 654-656 ◽  
pp. 1674-1677 ◽  
Author(s):  
Ying Chen ◽  
Satoshi Hirosawa ◽  
Shuichi Iwata
Keyword(s):  
Oxygen Concentration ◽  
First Principles ◽  
Formation Energy ◽  
Expansion Method ◽  
Sintered Magnets ◽  
Interfacial Phase ◽  
Cluster Expansion Method ◽  
Ordered Phases ◽  
Fcc Phase ◽  
The Stability

The NdOx phase formed at the Nd/Nd-Fe-B interface in Nd-sputtered Nd-Fe-B sintered magnets is paid rather attention recently due to its important role in coercivity generation of surface Nd-Fe-B grains. Its crystal structures have been reported to vary with the change of the oxygen concentration, and the disorder fcc phase derived from Nd2O3-C-type structure to be the main form of existence. To understand the formation mechanism of this fcc-NdOx interfacial phase, the stability of all oxygen concentration range of Nd-O system has been investigated from the first principles. Based on LSDA+U calculations for selected ordered phases at various oxygen concentration in Nd-O, the Cluster Expansion Method (CEM) is applied to evaluate the formation energy, density of states and other properties of disorder phase.

Influence of doping concentration on the elastic properties and electronic structure of the reduced Ce1−xMx O1.785 (M = Ti, Zr) from first principles

2021 ◽  
pp. 2150123
Author(s):  
Huiling Jia ◽  
Ru Jia ◽  
Jinxiu Wu ◽  
Xin Tan ◽  
Shiyang Sun
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Formation Energy ◽  
Elastic Moduli ◽  
Doping Concentration ◽  
Spin Splitting ◽  
Ductile Material ◽  
Degree Of Anisotropy ◽  
O Vacancy ◽  
Ti Doping

The effects of Ti and Zr doping concentrations on the mechanical properties and electronic structure of the reduced Ce[Formula: see text]M[Formula: see text]O[Formula: see text] were studied. The calculated results show that elastic moduli of Ce[Formula: see text]Ti[Formula: see text]O[Formula: see text] decreased, while those of Ce[Formula: see text]Zr[Formula: see text]O[Formula: see text] increased. Ce[Formula: see text]Ti[Formula: see text]O[Formula: see text] that undergoes structural transformation at 37.5 at.% Ti. Ce[Formula: see text]M[Formula: see text]O[Formula: see text] is ductile material. The degree of anisotropy of Ce[Formula: see text]Ti[Formula: see text]O[Formula: see text] decreased sharply at 25 at.% Ti, while that of Ce[Formula: see text]Zr[Formula: see text]O[Formula: see text] almost unchanged with the increase of Zr concentration. Ti and Zr doping has little effect on the electronic structure of the unreduced Ce[Formula: see text]M[Formula: see text]O2. Ti and Zr doping reduced the formation energy of O vacancy, and Ti doping was more conducive to the formation of O vacancy. The density of states of the reduced Ce[Formula: see text]M[Formula: see text]O[Formula: see text] exhibited spin splitting and was magnetic. Zr atom transferred 0.24–0.27 e more than Ti atom to the nearest O atoms, and Zr–O bond has stronger covalency and higher bond energy.

First-principles calculations of elastic moduli of Ti–Mo–Nb alloys using a cluster-plus-glue-atom model for stable solid solutions

2012 ◽  
Vol 48 (8) ◽  
pp. 3138-3146 ◽  
Author(s):  
Chong Zhang ◽  
Hua Tian ◽  
Chuanpu Hao ◽  
Jijun Zhao ◽  
Qing Wang ◽  
...  
Keyword(s):  
Solid Solutions ◽  
First Principles ◽  
Elastic Moduli ◽  
First Principles Calculations ◽  
Atom Model

Electronic and magnetic properties of F atoms adsorbed on TiO2:Mn(001) diluted magnetic semiconductor surfaces: First-principles calculations

2014 ◽  
Vol 28 (18) ◽  
pp. 1450096 ◽  
Author(s):  
Chunlei Wang ◽  
Dan Li ◽  
Yuan Niu ◽  
Hongmin Zhao ◽  
Chunjun Liang
Keyword(s):  
First Principles ◽  
Formation Energy ◽  
Diluted Magnetic Semiconductor ◽  
Magnetic Moments ◽  
Magnetic Semiconductor ◽  
First Principles Calculations ◽  
Ion Doping ◽  
Diluted Magnetic ◽  
The Stability ◽  
Mn Doped

We performed first-principles calculations for two Mn -doped structures in which Mn atoms substitute Ti atoms to determine whether (i) it is more conducive to Mn ion doping and (ii) ferromagnetism can occur in F adsorption anatase TiO 2 surfaces. Ferromagnetic (FM) coupling is more stable than antiferromagnetic (AFM) coupling for all doping configurations as the adsorption of F atoms on the surface significantly lowers the formation energy of the TiO 2: Mn system. The magnetic moments of the Mn ions are reduced, whereas those of O atoms on the surface are increased. The magnetic moment of the O atoms is mainly derived from the spin polarization p x and p y orbitals. F adsorption promotes doping of Mn atoms and to a certain extent improves the stability of the structure, magnetism and metallicity.

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