An origin of excess vibrational entropies at grain boundaries in Al, Si and MgO: a first-principles analysis with lattice dynamics

2021 ◽  
Author(s):  
T. Yokoi ◽  
K. Ikawa ◽  
A. Nakamura ◽  
K. Matsunaga
Keyword(s):  
Bond Length ◽  
Grain Boundaries ◽  
First Principles ◽  
Lattice Dynamics ◽  
Excess Entropy ◽  
First Principle ◽  
Length Changes

Excess vibrational entropies are examined by performing first-principle lattice dynamics for grain boundaries in MgO, Al and Si. Bond-length changes are critical for excess entropy, although their bonding nature is originally very different.

scholarly journals Ferroelectric switching in bilayer 3R MoS2 via interlayer shear mode driven by nonlinear phononics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jaehong Park ◽  
In Won Yeu ◽  
Gyuseung Han ◽  
Cheol Seong Hwang ◽  
Jung-Hae Choi
Keyword(s):  
First Principles ◽  
Lattice Dynamics ◽  
Shear Mode ◽  
First Principle ◽  
Interlayer Shear ◽  
Two Dimensional Materials ◽  
Dynamics Simulations ◽  
Anharmonic Coupling ◽  
Anharmonic Force ◽  
Ferroelectric Switching

Abstract We theoretically investigate the mechanism of ferroelectric switching via interlayer shear in 3R MoS2 using first principles and lattice dynamics calculations. First principle calculations show the prominent anharmonic coupling of the infrared inactive interlayer shear and the infrared active phonons. The nonlinear coupling terms generates an effective anharmonic force which drives the interlayer shear mode and lowers the ferroelectric switching barrier depending on the amplitude and polarization of infrared mode. Lattice dynamics simulations show that the interlayer shear mode can be coherently excited to the switching threshold by a train of infrared pulses polarized along the zigzag axis of MoS2. The results of this study indicate the possibility of ultrafast ferroelectricity in stacked two-dimensional materials from the control of stacking sequence.

scholarly journals Pressure effect of the mechanical, electronics and thermodynamic properties of Mg–B compounds A first-principles investigations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
GuoWei Zhang ◽  
Chao Xu ◽  
MingJie Wang ◽  
Ying Dong ◽  
FengEr Sun ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Boron Content ◽  
Structural Parameters ◽  
Debye Model ◽  
Total Density ◽  
First Principle ◽  
Volume Deformation ◽  
Temperature And Pressure ◽  
Total Density Of States

AbstractFirst principle calculations were performed to investigate the structural, mechanical, electronic properties, and thermodynamic properties of three binary Mg–B compounds under pressure, by using the first principle method. The results implied that the structural parameters and the mechanical properties of the Mg–B compounds without pressure are well matched with the obtainable theoretically simulated values and experimental data. The obtained pressure–volume and energy–volume revealed that the three Mg–B compounds were mechanically stable, and the volume variation decreases with an increase in the boron content. The shear and volume deformation resistance indicated that the elastic constant Cij and bulk modulus B increased when the pressure increased up to 40 GPa, and that MgB7 had the strongest capacity to resist shear and volume deformation at zero pressure, which indicated the highest hardness. Meanwhile, MgB4 exhibited a ductility transformation behaviour at 30 GPa, and MgB2 and MgB7 displayed a brittle nature under all the considered pressure conditions. The anisotropy of the three Mg–B compounds under pressure were arranged as follows: MgB4 > MgB2 > MgB7. Moreover, the total density of states varied slightly and decreased with an increase in the pressure. The Debye temperature ΘD of the Mg–B compounds gradually increased with an increase in the pressure and the boron content. The temperature and pressure dependence of the heat capacity and the thermal expansion coefficient α were both obtained on the basis of Debye model under increased pressure from 0 to 40 GPa and increased temperatures. This paper brings a convenient understanding of the magnesium–boron alloys.

scholarly journals Coupling of lattice dynamics and configurational disorder in metal deficient Al1−δB2 from first-principles

2021 ◽  
Vol 130 (1) ◽  
pp. 015110
Author(s):  
Erik Johansson ◽  
Fredrik Eriksson ◽  
Annop Ektarawong ◽  
Johanna Rosen ◽  
Björn Alling
Keyword(s):  
First Principles ◽  
Lattice Dynamics

First-principles study of lattice dynamics and diffusion inDO3-typeFe3Si

2006 ◽  
Vol 73 (17) ◽  
Author(s):  
S. Dennler ◽  
J. Hafner
Keyword(s):  
First Principles ◽  
Lattice Dynamics ◽  
First Principles Study ◽  
And Diffusion

scholarly journals The thermal stability of FAPbBr3 nanocrystals from temperature-dependent photoluminescence and first-principles calculations

RSC Advances ◽  
2020 ◽  
Vol 10 (72) ◽  
pp. 44373-44381
Author(s):  
Xiaozhe Wang ◽  
Qi Wang ◽  
Zhijun Chai ◽  
Wenzhi Wu
Keyword(s):  
First Principles ◽  
First Principle ◽  
First Principles Calculations ◽  
Temperature Dependent ◽  
Time Resolved ◽  
First Principle Calculations ◽  
Steady State Time ◽  
Time Resolved Photoluminescence ◽  
Thermal Stability Of ◽  
Temperature Dependent Photoluminescence

The thermal properties of FAPbBr3 perovskite nanocrystals (PNCs) is investigated by use of temperature-dependent steady-state/time-resolved photoluminescence and first-principle calculations.

scholarly journals Lattice dynamics effects on finite-temperature stability of R 1−Fe (R = Y, Ce, Nd, Sm, and Dy) alloys from first principles

2021 ◽  
pp. 159754
Author(s):  
Guangzong Xing ◽  
Takahiro Ishikawa ◽  
Yoshio Miura ◽  
Takashi Miyake ◽  
Terumasa Tadano
Keyword(s):  
First Principles ◽  
Finite Temperature ◽  
Lattice Dynamics ◽  
Temperature Stability

Accelerated materials design of Na0.5Bi0.5TiO3 oxygen ionic conductors based on first principles calculations

2015 ◽  
Vol 17 (27) ◽  
pp. 18035-18044 ◽  
Author(s):  
Xingfeng He ◽  
Yifei Mo
Keyword(s):  
First Principles ◽  
Materials Design ◽  
First Principle ◽  
First Principles Calculations ◽  
Ionic Conductors ◽  
First Principle Calculations

First principle calculations are performed to accelerate the design of new oxygen ionic conductors.

Dynamic Stability of Ni FCC Crystal under Isotropic Tension

2013 ◽  
Vol 592-593 ◽  
pp. 47-50
Author(s):  
Petr Řehák ◽  
Miroslav Černý
Keyword(s):  
Dynamic Stability ◽  
Wave Vector ◽  
First Principles ◽  
Lattice Dynamics ◽  
Harmonic Approximation ◽  
Tensile Loading ◽  
The Other ◽  
Other Hand ◽  
Critical Strains

Lattice dynamics and stability of fcc crystal of Ni under isotropic (hydrostatic) tensile loading are studied from first principles using supercell method and a harmonic approximation. According to the results, strength of the crystal is determined by occurrence of an instability related to soft phonons with finite wave vector. On the other hand, the critical strains and stresses associated with such instabilities are only slightly lower than those related to the volumetric instability.

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