Pressure-induced vibrational and superconducting properties of lanthanum hydrides from first principles calculations

2015 ◽  
Vol 93 (12) ◽  
pp. 1630-1637 ◽  
Author(s):  
De-Chun He ◽  
Han-Xiao Shao ◽  
Yong-Kai Wei
Keyword(s):  
First Principles ◽  
Phonon Dispersion ◽  
Theoretical Calculations ◽  
Underlying Mechanism ◽  
Face Centered Cubic ◽  
Superconducting Transition ◽  
First Principles Calculations ◽  
Superconducting Properties ◽  
Hydrogen Atoms ◽  
Octahedral Sites

Pressure-induced vibrational and superconducting properties of lanthanum hydrides (LaH2 and LaH3) have been studied using first principles calculations. It is found that LaH2 and LaH3 are dynamically stable in the pressure ranges of 0–39 GPa and 4–35 GPa, respectively. The character of phonon dispersion curves for LaH2 and LaH3 is analyzed under pressure. The zone-center phonon mode eigen displacements that represent infrared and Raman activity are also obtained, which are essential to the analysis of spectral experiments. The calculations based on Bardeen–Cooper–Schrieffer theory indicate that LaH2 almost has no superconducting behavior even under pressure, in reasonable agreement with previous theoretical calculations and experiments. Whereas, LaH3 presents a considerable high superconducting transition temperature (Tc) at the onset of the face centered cubic structure, while it decreases exponentially under further compression up to 25 GPa and finally almost approaches zero. Further analysis indicates that the underlying mechanism of these two distinct superconducting behaviors are closely related to the hybridization between the HO-s state and La-d state. The mode Grüneisen parameters of two hydrides are also analyzed under 35 GPa, finding that the hydrogen atoms at octahedral sites are responsible for the superconducting properties of LaH3, and in fact, the unobserved superconducting behavior in LaH2 can be interpreted as the absence of hydrogen at octahedral sites compared with LaH3.

scholarly journals Relationship between the Behavior of Hydrogen and Hydrogen Bubble Nucleation in Vanadium

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 322
Author(s):  
Zhengxiong Su ◽  
Sheng Wang ◽  
Chenyang Lu ◽  
Qing Peng
Keyword(s):  
Hydrogen Atom ◽  
First Principles ◽  
Bound States ◽  
Hydrogen Molecule ◽  
Vacancy Cluster ◽  
Bubble Nucleation ◽  
Hydrogen Bubble ◽  
First Principles Calculations ◽  
Hydrogen Atoms ◽  
Macroscopic Deformation

Hydrogen plays a significant role in the microstructure evolution and macroscopic deformation of materials, causing swelling and surface blistering to reduce service life. In the present work, the atomistic mechanisms of hydrogen bubble nucleation in vanadium were studied by first-principles calculations. The interstitial hydrogen atoms cannot form significant bound states with other hydrogen atoms in bulk vanadium, which explains the absence of hydrogen self-clustering from the experiments. To find the possible origin of hydrogen bubble in vanadium, we explored the minimum sizes of a vacancy cluster in vanadium for the formation of hydrogen molecule. We show that a freestanding hydrogen molecule can form and remain relatively stable in the center of a 54-hydrogen atom saturated 27-vacancy cluster.

scholarly journals Rectifying Performance of Heterojunction Based on α-Borophene Nanoribbons with Edge Passivation

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Guoliang Yu ◽  
Wence Ding ◽  
Xianbo Xiao ◽  
Xiaobo Li ◽  
Guanghui Zhou
Keyword(s):  
Electronic Transport ◽  
First Principles ◽  
First Principles Calculations ◽  
Zigzag Edge ◽  
Hydrogen Atoms ◽  
Rectification Effect ◽  
Structural Details ◽  
Potential Applications ◽  
Matching Degree ◽  
The Right

Abstract We propose a planar model heterojunction based on α-borophene nanoribbons and study its electronic transport properties. We respectively consider three types of heterojunctions. Each type consists of two zigzag-edge α-borophene nanoribbons (Z αBNR), one is metallic with unpassivated or passivated edges by a hydrogen atom (1H-Z αBNR) and the other is semiconducting with the edge passivated by two hydrogen atoms (2H-Z αBNR) or a single nitrogen atom (N-Z αBNR). Using the first-principles calculations combined with the nonequilibrium Green’s function, we observe that the rectifying performance depends strongly on the atomic structural details of a junction. Specifically, the rectification ratio of the junction is almost unchanged when its left metallic ribbon changes from ZBNR to 1H-Z αBNR. However, its ratio increases from 120 to 240 when the right semiconducting one varies from 2H-Z αBNR to N-Z αBNR. This rectification effect can be explained microscopically by the matching degree the electronic bands between two parts of a junction. Our findings imply that the borophene-based heterojunctions may have potential applications in rectification nano-devices.

scholarly journals Strain sensitivity and superconducting properties of Nb3Sn from first principles calculations

2013 ◽  
Vol 25 (13) ◽  
pp. 135702 ◽  
Author(s):  
G De Marzi ◽  
L Morici ◽  
L Muzzi ◽  
A della Corte ◽  
M Buongiorno Nardelli
Keyword(s):  
First Principles ◽  
Strain Sensitivity ◽  
First Principles Calculations ◽  
Superconducting Properties

First-principles study on the stability and magnetoelectric properties of multiferroic materials XTiO3 (X = Mn, Fe, Co, Ni)

2018 ◽  
Vol 32 (09) ◽  
pp. 1850105 ◽  
Author(s):  
Xing-Yuan Chen ◽  
Guo-Xia Lai ◽  
Di Gu ◽  
Wei-Ling Zhu ◽  
Tian-Shu Lai ◽  
...  
Keyword(s):  
Magnetic Property ◽  
First Principles ◽  
Phonon Dispersion ◽  
Critical Conditions ◽  
First Principles Calculations ◽  
Multiferroic Materials ◽  
Equilibrium Conditions ◽  
Magnetoelectric Properties ◽  
Strong Hybridization ◽  
The Stability

The XTiO3 (X = Mn, Fe, Co and Ni) materials with R3c structure could be grown under critical conditions based on first-principles calculations and thermodynamic stability analysis. FeTiO3 and MnTiO3 could be synthesized relatively easily under metal-rich and O-poor conditions, while NiTiO3 could be stable under Ni-rich, O-rich and Ti-poor conditions. The predicted R3c CoTiO3 under thermodynamic equilibrium conditions is suggested to be synthesized under Co-rich, O-rich and Ti-poor conditions, but the calculated phonon dispersion indicates R3c CoTiO3 becomes unstable under the dynamical conditions. The ferroelectric behavior in the XTiO3 (X = Mn, Fe, Co and Ni) system could be dominated by the Ti ion with d0 state and the strong hybridization between Ti and O, while the magnetic property is mainly caused by the contribution of 3d transition metal.

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.

Optical properties of prodigiosin and obatoclax: action spectroscopy and theoretical calculations

2015 ◽  
Vol 17 (39) ◽  
pp. 25946-25955 ◽  
Author(s):  
Evangeline Drink ◽  
Philippe Dugourd ◽  
Elise Dumont ◽  
Nils Aronssohn ◽  
Rodolphe Antoine ◽  
...  
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Theoretical Calculations ◽  
Ion Binding ◽  
First Principles Calculations ◽  
Action Spectroscopy ◽  
Counter Ion ◽  
Counter Ion Binding

Action spectroscopy and first principles calculations are performed to characterize the optical properties of prodigiosin, and its sensibility to protonation, counter-ion binding, and isomerization.

Surface phonon dispersion on hydrogen-terminated Si(110)-(1 × 1) surfaces studied by first-principles calculations

2015 ◽  
Vol 143 (21) ◽  
pp. 214702 ◽  
Author(s):  
Stephane Yu Matsushita ◽  
Chunping Hu ◽  
Erina Kawamoto ◽  
Hiroki Kato ◽  
Kazuyuki Watanabe ◽  
...  
Keyword(s):  
First Principles ◽  
Phonon Dispersion ◽  
First Principles Calculations ◽  
Surface Phonon
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