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

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.

First-Principles Investigations of Structural Stability of LuN

2013 ◽  
Vol 690-693 ◽  
pp. 559-563 ◽  
Author(s):  
Xiao Cui Yang ◽  
En Jie Zhang ◽  
Hong Yuan Ma ◽  
Jun Ping Xiao
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Stability ◽  
First Principles ◽  
Phonon Dispersion ◽  
Type Structure ◽  
First Principles Calculations ◽  
Phonon Dispersion Curves ◽  
Elevated Pressures ◽  
Cscl Type

An investigation on structural stability of LuN under high pressure has been conducted using first-principles calculations. At elevated pressures LuN is predicted to undergo a phase transition from NaCl-type structure (B1) into CsCl-type structure (B2). The predicted transition pressure is 220 GPa. The phonon dispersion curves of B1 and B2 at 0 and 220 GPa are presented.

scholarly journals Investigations on Cmc21-Si2P2X structures and physical properties by first-principles calculations

2021 ◽  
Vol 24 (4) ◽  
pp. 43602
Author(s):  
R. Yang ◽  
X. Gao ◽  
F. Wu ◽  
Q. Wei ◽  
M. Xue
Keyword(s):  
Optical Properties ◽  
Sound Velocity ◽  
First Principles ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Elastic Stability ◽  
First Principles Calculations ◽  
Shear Moduli ◽  
Longitudinal Sound Velocity ◽  
Bandgap Semiconductors

The new structures, Cmc21-Si2P2X (X=S, Se, Te, and Po), are predicted, and their mechanical, electronic and optical properties are investigated with the density functional theory, by first principles calculations. The elastic constants of the four compounds are calculated by the stress-strain method. The calculations of the elastic stability criteria and phonon dispersion spectra imply that they are mechanically and dynamically stable at zero pressure. The mechanical parameters, such as shear moduli G, bulk moduli B, Young's moduli E and Poisson's ratios v are evaluated by the Voigt-Reuss-Hill approach. The Cmc21-Si2P2X has the largest hardness due to the largest Young's modulus in the four compounds, and it is a covalent crystal. The anisotropies of their mechanical properties are also analyzed. The band structures and densities of states, which are calculated by using HSE06, show that Cmc21-Si2P2X compounds are indirect bandgap semiconductors, and the values of the band gaps decrease with increasing atomic number from S, Se, Te, to Po. In addition, the longitudinal sound velocity and transverse sound velocity for Cmc21-Si2P2X have been investigated. The dielectric constant, electron energy loss, refractive index, reflectivity, absorption and conductivity are analyzed to gain the optical properties of Si2P2X.

scholarly journals Obvious Surface States Connecting to the Projected Triple Points in NaCl’s Phonon Dispersion

2021 ◽  
Vol 9 ◽  
Author(s):  
Li Zhang ◽  
Fang Fang ◽  
Lixin Cheng ◽  
Huiming Lin ◽  
Kai Wang
Keyword(s):  
Computer Technology ◽  
Triple Point ◽  
First Principles ◽  
Phonon Dispersion ◽  
Surface States ◽  
Theoretical Chemistry ◽  
First Principles Calculations ◽  
Nodal Lines ◽  
Topological Materials ◽  
Speed And Accuracy

With the development of computer technology and theoretical chemistry, the speed and accuracy of first-principles calculations have significantly improved. Using first-principles calculations to predict new topological materials is a hot research topic in theoretical and computational chemistry. In this work, we focus on a well-known material, sodium chloride (NaCl), and propose that the triple point (TP), quadratic contact triple point (QCTP), linear and quadratic nodal lines can be found in the phonon dispersion of NaCl with Fm3¯ m type structure. More importantly, we propose that the clear surface states connected to the projected TP and QCTP are visible on the (001) surface. It is hoped that further experimental investigation and verification for these properties as mentioned above.

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.

First-principles screening calculation of the surface phonon dispersion curves at the (100) surface of sodium

1990 ◽  
Vol 7 (3) ◽  
pp. 215-218
Author(s):  
A.A. Quong ◽  
R.F. Wallis ◽  
A.A. Maradudin ◽  
J.A. Gaspar ◽  
A.G. Eguiluz ◽  
...  
Keyword(s):  
First Principles ◽  
Phonon Dispersion ◽  
Dispersion Curves ◽  
Phonon Dispersion Curves ◽  
Surface Phonon
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