scholarly journals Density-functional investigation of the rhombohedral to simple-cubic phase transition of arsenic

2008 ◽  
Vol 78 (17) ◽  
Author(s):  
Patricia Silas ◽  
Jonathan R. Yates ◽  
Peter D. Haynes
Keyword(s):  
Phase Transition ◽  
Density Functional ◽  
Cubic Phase ◽  
Simple Cubic ◽  
Functional Investigation

Rhombohedral to simple-cubic phase transition in arsenic under pressure

1990 ◽  
Vol 41 (9) ◽  
pp. 5535-5543 ◽  
Author(s):  
H. J. Beister ◽  
K. Strössner ◽  
K. Syassen
Keyword(s):  
Phase Transition ◽  
Cubic Phase ◽  
Simple Cubic

First-Principles Calculations of Structural Changes Induced by Oxygen Vacancies in Tetragonal Phase BaTiO3

2011 ◽  
Vol 485 ◽  
pp. 19-22
Author(s):  
Yoshiki Iwazaki ◽  
Tatsuo Sakashita ◽  
Toshimasa Suzuki ◽  
Youichi Mizuno ◽  
Shinji Tsuneyuki
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
First Principles ◽  
Tetragonal Phase ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Structural Changes ◽  
Cubic Phase ◽  
First Principles Calculations ◽  
Functional Theory

Structural changes induced by oxygen vacancies in tetragonal phase BaTiO3are studied with first principles calculations within density functional theory. In our calculations, the incorporation of oxygen vacancies greatly decreases c/a ratio of the tetragonal phase BaTiO3, and a phase transition from tetragonal to cubic phase occurs when the incorporation of the oxygen vacancies reaches about 4%. Our results also shows that the generation of the oxygen vacancies slightly increases the volume of BaTiO3, and the increases are typically less than 0.5% even in heavily reduced conditions.

scholarly journals Pressure-induced phase transitions and superconductivity in a black phosphorus single crystal

2018 ◽  
Vol 115 (40) ◽  
pp. 9935-9940 ◽  
Author(s):  
Xiang Li ◽  
Jianping Sun ◽  
Prashant Shahi ◽  
Miao Gao ◽  
Allan H. MacDonald ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Single Crystal ◽  
Transport Properties ◽  
Density Functional ◽  
Black Phosphorus ◽  
Cubic Phase ◽  
Superconducting Transition ◽  
Quantum Oscillations ◽  
Mr Effect

We report a thorough study of the transport properties of the normal and superconducting states of black phosphorus (BP) under magnetic field and high pressure with a large-volume apparatus that provides hydrostatic pressure to induce transitions from the layered A17 phase to the layered A7 phase and to the cubic phase of BP. Quantum oscillations can be observed atP≥ 1 GPa in both resistivity and Hall voltage, and their evolutions with pressure in the A17 phase imply a continuous enlargement of Fermi surface. A significantly large magnetoresistance (MR) at low temperatures is observed in the A7 phase that becomes superconducting below a superconducting transition temperatureTc∼ 6–13 K.Tcincreases continuously with pressure on crossing the A7 to the cubic phase boundary. The strong MR effect can be fit by a modified Kohler’s rule. A correlation betweenTcand fitting parameters suggests that phonon-mediated interactions play dominant roles in driving the Cooper pairing, which is further supported by our density functional theory (DFT) calculations. The change of effective carrier mobility in the A17 phase under pressure derived from the MR effect is consistent with that obtained from the temperature dependence of the quantum oscillations. In situ single-crystal diffraction under high pressure indicates a total structural reconstruction instead of simple stretching of the A17 phase layers in the A17-to-A7-phase transition. This finding helps us to interpret transport properties on crossing the phase transition under high pressure.

scholarly journals Ab Initio Study of Martensitic Transformation in NiTiPt High Temperature Shape Memory Alloys

2021 ◽  
Vol 11 (15) ◽  
pp. 6878
Author(s):  
Xiaolan Yang ◽  
Jiaxiang Shang
Keyword(s):  
Phase Transition ◽  
Martensitic Transformation ◽  
Electronic Structures ◽  
Density Functional ◽  
Martensite Phase ◽  
Computational Results ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Phase Transition Temperatures ◽  
Martensite Structure

The crystal structures and martensitic transformation of Ti50Ni50−xPtx alloys (x = 0, 6.25, 8.33, 10.42, 12.5, 18.75, 25) were studied by means of density functional theory (DFT). The computational results indicate that the lattice parameters of Ti-Ni-Pt alloys continuously increase with increasing the Pt content. It is found that at ≤ 12.5 at.% Pt, the martensite structure is monoclinic B19′ phase, and the energy differences between parent and martensite phases (ΔE) decrease slightly with a minimum observed at 6.25 at.% Pt. However, when the Pt content is increased to around 15 at.%, the most stable martensite phase is the orthorhombic B19 structure, and the ΔE increases sharply with Pt concentration. It was found that the phase transition temperatures are closely related to the energy differences ΔE between parent and martensite phases. The electronic structures of martensite B19 and B19′ phases are also discussed.

scholarly journals Liquid–liquid phase transition in hydrogen by coupled electron–ion Monte Carlo simulations

2016 ◽  
Vol 113 (18) ◽  
pp. 4953-4957 ◽  
Author(s):  
Carlo Pierleoni ◽  
Miguel A. Morales ◽  
Giovanni Rillo ◽  
Markus Holzmann ◽  
David M. Ceperley
Keyword(s):  
Phase Transition ◽  
Monte Carlo ◽  
Density Functional ◽  
Fluid Phase ◽  
Transition Line ◽  
Energy Applications ◽  
First Order Phase Transition ◽  
Fundamental Research ◽  
Diamond Anvil ◽  
First Order Phase

The phase diagram of high-pressure hydrogen is of great interest for fundamental research, planetary physics, and energy applications. A first-order phase transition in the fluid phase between a molecular insulating fluid and a monoatomic metallic fluid has been predicted. The existence and precise location of the transition line is relevant for planetary models. Recent experiments reported contrasting results about the location of the transition. Theoretical results based on density functional theory are also very scattered. We report highly accurate coupled electron–ion Monte Carlo calculations of this transition, finding results that lie between the two experimental predictions, close to that measured in diamond anvil cell experiments but at 25–30 GPa higher pressure. The transition along an isotherm is signaled by a discontinuity in the specific volume, a sudden dissociation of the molecules, a jump in electrical conductivity, and loss of electron localization.

Density Functional Investigation on Li2MnO3

2012 ◽  
Vol 24 (21) ◽  
pp. 4242-4251 ◽  
Author(s):  
Ruijuan Xiao ◽  
Hong Li ◽  
Liquan Chen
Keyword(s):  
Density Functional ◽  
Functional Investigation
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