Lattice distortion in high‐entropy carbide ceramics from first‐principles calculations

2021 ◽  
Author(s):  
Shijun Zhao
Keyword(s):  
First Principles ◽  
Lattice Distortion ◽  
First Principles Calculations ◽  
High Entropy ◽  
Carbide Ceramics

Phase decomposition and strengthening in HfNbTaTiZr high entropy alloy from first-principles calculations

2021 ◽  
pp. 117582
Author(s):  
Shu-Ming Chen ◽  
Ze-Jun Ma ◽  
Shi Qiu ◽  
Lian-Ji Zhang ◽  
Shang-Zhou Zhang ◽  
...  
Keyword(s):  
First Principles ◽  
High Entropy Alloy ◽  
Phase Decomposition ◽  
First Principles Calculations ◽  
High Entropy

scholarly journals Effect of Defects on Spontaneous Polarization in Pure and Doped LiNbO3: First-Principles Calculations

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 100 ◽  
Author(s):  
Weiwei Wang ◽  
Dahuai Zheng ◽  
Mengyuan Hu ◽  
Shahzad Saeed ◽  
Hongde Liu ◽  
...  
Keyword(s):  
Spontaneous Polarization ◽  
First Principles ◽  
Density Functional ◽  
Lattice Distortion ◽  
Stable Structure ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Specific Configuration ◽  
The Relationship

Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory (DFT), the specific configuration of the four lithium vacancies of LN were explored. The results indicated the most stable structure consisted of two lithium vacancies as the first neighbors and the other two as the second nearest neighbors of Nb anti-site in pure LN, and a similar stable structure was found in the doped LN. We found that the defects dipole moment has no direct contribution to the crystal polarization. Spontaneous polarization is more likely due to the lattice distortion of the crystal. This was verified in the defects structure of Mg2+, Sc3+, and Zr4+ doped LN. The conclusion provides a new understanding about the relationship between defect clusters and crystal polarization.

scholarly journals Identification of a monoclinic metallic state in VO2 from a modified first-principles approach

2019 ◽  
Vol 33 (12) ◽  
pp. 1950148
Author(s):  
Yongcheng Liang ◽  
Ping Qin ◽  
Zhiyong Liang ◽  
Lizhen Zhang ◽  
Xun Yuan ◽  
...  
Keyword(s):  
First Principles ◽  
Lattice Distortion ◽  
Insulator Transition ◽  
Metallic State ◽  
Strongly Correlated ◽  
Electron Systems ◽  
First Principles Calculations ◽  
Monoclinic Structure ◽  
Metal Insulator Transition ◽  
Metal Insulator

Metal-insulator transition (MIT) underlies many remarkable and technologically important phenomena in VO2. Even though its monoclinic structure had before been the reserve of the insulating state, recent experiments have observed an unexpected monoclinic metallic state. Here, we use a modified approach combining first-principles calculations with orbital-biased potentials to reproduce the correct stability ordering and electronic structures of different phases of VO2. We identify a ferromagnetic monoclinic metal that is likely to be the experimentally observed mysterious metastable state. Furthermore, the calculations show that an isostructural insulator-metal electronic transition is followed by the lattice distortion from the monoclinic structure to the rutile one. These results not only explain the experimental observations of the monoclinic metallic state and the decoupled structural and electronic transitions of VO2, but also provide a useful understanding for the metal-insulator transition in other strongly correlated d electron systems.

scholarly journals An investigation of high entropy alloy conductivity using first-principles calculations

2021 ◽  
Vol 119 (12) ◽  
pp. 121903
Author(s):  
Vishnu Raghuraman ◽  
Yang Wang ◽  
Michael Widom
Keyword(s):  
First Principles ◽  
High Entropy Alloy ◽  
First Principles Calculations ◽  
High Entropy

scholarly journals Mn ions' site and valence in PbTiO3 based on the native vacancy defects

2021 ◽  
Vol 24 (2) ◽  
pp. 23705
Author(s):  
H. Xin ◽  
Q. Pang ◽  
D. L. Gao ◽  
L. Li ◽  
P. Zhang ◽  
...  
Keyword(s):  
First Principles ◽  
Formation Energy ◽  
Lattice Distortion ◽  
First Principles Calculations ◽  
Equilibrium Conditions ◽  
Vacancy Defects ◽  
Domain Movement ◽  
Ion Substitution ◽  
A Site ◽  
Mn Doped

Mn ions' doping site and valence were studied in PbTiO3 (PT) with the native vacancy defects by the first-principles calculations. Firstly, the native vacancy defects of Pb, O and Ti in PT were investigated and it was found that Pb vacancy is preferred to others. And then the growth of Mn doped PT should be preferred to Mn ion substituting for an A-site Pb ion with +3 valence when Pb is deficient under equilibrium conditions driven solely by minimization of the formation energy, and this could result in a larger lattice distortion of PT. In addition, when Mn enters the Pb site, the electronegativity of O becomes weaker which makes the domain movement easier in PT to improve the performance of PT, while Mn ion substitution for a B-site Ti ion is the opposite.

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