Nonlinear propagating modes beyond the phonons in fluorite-structured crystals

AbstractThe vibrational energy of crystals is known to propagate in a fixed number of phonon branches allowed by symmetry. In the realm of nonlinear dynamics, however, additional nonlinear propagating modes are possible. Nonlinear propagating modes have unique properties that are important in many disciplines including optical communications, conducting polymers, biology, magnetism, and nuclear physics. Yet, despite the crucial importance of crystal lattice vibrations in fundamental and applied science, such additional propagating modes have not been observed in ordinary crystals. Here, we show that propagating modes exist beyond the phonons in fluorite-structured thoria, urania, and natural calcium fluoride using neutron scattering and first-principles calculations. These modes are observed at temperatures ranging from 5 K up to 1200 K, extend to frequencies 30–40% higher than the maximum phonon frequency, and travel at velocities comparable to or higher than the fastest phonon. The nonlinear origin of the modes is explained in part via perturbation theory, which approximately accounts for nonlinearity. Given that these modes are still clearly observed at 5 K, they are likely an inherent feature of the quantum ground state. The existence of these waves in three-dimensional crystals may have ramifications for material properties.

Download Full-text

Preferential proton conduction along a three-dimensional dopant network in yttrium-doped barium zirconate: a first-principles study

Journal of Materials Chemistry A ◽

10.1039/c8ta08283a ◽

2018 ◽

Vol 6 (45) ◽

pp. 22721-22730 ◽

Cited By ~ 8

Author(s):

Kazuaki Toyoura ◽

Weijie Meng ◽

Donglin Han ◽

Tetsuya Uda

Keyword(s):

First Principles ◽

Three Dimensional ◽

Proton Conduction ◽

Atomic Scale ◽

Barium Zirconate ◽

First Principles Calculations ◽

First Principles Study

The atomic-scale picture of proton conduction in highly doped barium zirconate has theoretically been clarified using first-principles calculations.

Download Full-text

Electronic structure, optical and dielectric properties of BaTiO3/CaTiO3/SrTiO3 ferroelectric superlattices from first-principles calculations

Journal of Materials Chemistry C ◽

10.1039/c5tc01622c ◽

2015 ◽

Vol 3 (33) ◽

pp. 8625-8633 ◽

Cited By ~ 49

Author(s):

Bingcheng Luo ◽

Xiaohui Wang ◽

Enke Tian ◽

Guowu Li ◽

Longtu Li

Keyword(s):

Electronic Structure ◽

Dielectric Properties ◽

Thermodynamic Properties ◽

First Principles ◽

Lattice Vibrations ◽

First Principles Calculations ◽

Optical Dielectric

The electronic structure, lattice vibrations, and optical, dielectric and thermodynamic properties of BaTiO3/CaTiO3/SrTiO3 (BT/CT/ST) ferroelectric superlattices are calculated by using first-principles calculations.

Download Full-text

Three-dimensional metallic carbon allotropes with superhardness

Nanotechnology Reviews ◽

10.1515/ntrev-2021-0079 ◽

2021 ◽

Vol 10 (1) ◽

pp. 1266-1276

Author(s):

Qingyang Fan ◽

Heng Liu ◽

Li Jiang ◽

Wei Zhang ◽

Yanxing Song ◽

...

Keyword(s):

Fermi Level ◽

Dynamic Stability ◽

First Principles ◽

Mechanical Stability ◽

Three Dimensional ◽

First Principles Calculations ◽

Charge Densities ◽

Carbon Allotropes

Abstract Three novel three-dimensional orthorhombic carbon phases are proposed based on first-principles calculations in this work. These phases possess dynamic stability and mechanical stability and are theoretically more favorable in energy compared to most other carbon allotropes. The hardness levels of oP-C16, oP-C20, and oP-C24 are 47.5, 49.6, and 55.3 GPa, respectively, which are greater than those of T10, T18, and O12 carbon. In addition, although oP-C16, oP-C20, and oP-C24 are metals, their ideal shear strengths are also greater than those of common metals such as Cu, Fe, and Al. Due to p y electrons crossing the Fermi level, oP-C16, oP-C20, and oP-C24 show metallicity, and their charge densities of the band decomposition suggest that all the conductive directions of oP-C16, oP-C20, and oP-C24 are exhibited along the a- and b-axis, similar to C5.

Download Full-text

Structural Evolution, Redox Mechanism, and Ionic Diffusion in Rhombohedral Na2FeFe(CN)6 for Sodium-Ion Batteries: First-Principles Calculations

Journal of The Electrochemical Society ◽

10.1149/1945-7111/ac49cf ◽

2022 ◽

Author(s):

Ya-Ping Wang ◽

B. P. Hou ◽

Xin-Rui Cao ◽

Shunqing Wu ◽

Zi-Zhong Zhu

Keyword(s):

First Principles ◽

Rational Design ◽

Low Cost ◽

Magnetic Moments ◽

Three Dimensional ◽

Structural Evolution ◽

Sodium Ion ◽

High Rate ◽

Sodium Ion Batteries ◽

First Principles Calculations

Abstract Prussian blue analogs (Na2FeFe(CN)6) have been regarded as potential cathode materials for sodium-ion batteries (SIBs) due to their low-cost iron resources and open framework. Herein, the detailed first-principles calculations have been performed to investigate the electrochemical properties of NaxFeFe(CN)6 during Na ion extraction. The material undergoes a phase transition from a dense rhombohedral to open cubic structure upon half-desodiation, which is resulted from competition of the Na−N Coulomb attraction and d−π covalent bonding of Fe−N. The analyses on the density of states, magnetic moments and Bader charges of NaxFeFe(CN)6 reveal that there involve in the successive redox reactions of high-spin Fe2+/Fe3+ and low-spin Fe2+/Fe3+ couples during desodiation. Moreover, the facile three-dimensional diffusion channels for Na+ ions exhibit low diffusion barriers of 0.4 eV ~ 0.44 eV, which ensures a rapid Na+ transport in the NaxFeFe(CN)6 framework, contributing to high rate performance of the battery. This study gives a deeper understanding of the electrochemical mechanisms of NaxFeFe(CN)6 during Na+ extraction, which is beneficial for the rational design of superior PBA cathodes for SIBs.

Download Full-text

Confinement Effect Driven Quantum Spin Hall Effect in Monolayer AuTe2Cl

SPIN ◽

10.1142/s2010324719400149 ◽

2019 ◽

Vol 09 (04) ◽

pp. 1940014

Author(s):

Guyue Zhong ◽

Q. Xie ◽

Gang Xu

Keyword(s):

First Principles ◽

Three Dimensional ◽

Bulk Sample ◽

Quantum Spin ◽

Confinement Effect ◽

First Principles Calculations ◽

Quantum Spin Hall Effect ◽

Band Inversion ◽

Topological Semimetal ◽

Quantum Spin Hall

Based on first-principles calculations, we predict that the monolayer AuTe2Cl is a quantum spin Hall (QSH) insulator with a topological band gap about 10 meV. The three-dimensional (3D) AuTe2Cl is a topological semimetal that can be viewed as the monolayer stacking along [Formula: see text] axis. By studying the energy-level distribution of [Formula: see text] orbitals of Te atoms for the bulk and the monolayer, we find that the confinement effect driven [Formula: see text] band inversion is responsible for the topological nontrivial nature of monolayer. Since 3D bulk AuTe2Cl has already been experimentally synthesized, we expect that monolayer AuTe2Cl can be exfoliated from a bulk sample and the predicted QSH effect can be observed.

Download Full-text

Structural, electronic, sodium diffusion and elastic properties of Na–P alloy anode for Na-ion batteries: Insight from first-principles calculations

Modern Physics Letters B ◽

10.1142/s0217984916503851 ◽

2016 ◽

Vol 30 (32n33) ◽

pp. 1650385 ◽

Cited By ~ 1

Author(s):

Huansheng Lu ◽

Bo Xu ◽

Jing Shi ◽

Musheng Wu ◽

Yinquan Hu ◽

...

Keyword(s):

Elastic Properties ◽

First Principles ◽

Anode Materials ◽

Three Dimensional ◽

Lithium Ion ◽

Sodium Concentration ◽

First Principles Calculations ◽

High Sodium ◽

Intermediate Phases ◽

Diffusion Dynamics

Sodium-ion batteries (NIBs) as an alternative to lithium-ion batteries (LIBs) have recently received great attentions because of the relatively high abundance of sodium. Searching for suitable anode materials has always been a hot topic in the field of NIB study. Recent reports show that phosphorus-based materials are potential as the anode materials for NIBs. Using first-principles calculations, herein, we study the atomic and electronic structures, diffusion dynamics and intrinsic elastic properties of various Na–P alloy compounds (NaP5, Na3P[Formula: see text], NaP and Na3P) as the intermediate phases during Na extraction/insertion in phosphorus-based anode materials. It is found that all the crystalline phases of Na–P alloy phases considered in our study are semiconductors with band gaps larger than that of black phosphorus (BP). The calculations of Na diffusion dynamics indicate a relatively fast Na diffusion in these materials, which is important for good rate performance. In addition, the diffusion channels of sodium ions are one-dimensional in NaP5 phase and three-dimensional in other three phases (Na3P[Formula: see text], NaP and Na3P). Elastic constant calculations indicate that all four phases are mechanically stable. Among them, however, NaP5, Na3P[Formula: see text] and NaP alloy phases are ductile, while the fully sodiated phase Na3P is brittle. In order to improve the electrochemical performance of Na–P alloy anodes for NIBs, thus, promoting ductility of Na–P phase with high sodium concentration may be an effective way.

Download Full-text

Two-dimensional cyanates: stabilization through hydrogenation

Physical Chemistry Chemical Physics ◽

10.1039/c6cp02613c ◽

2016 ◽

Vol 18 (21) ◽

pp. 14662-14666 ◽

Cited By ~ 10

Author(s):

Leonidas Tsetseris

Keyword(s):

First Principles ◽

Three Dimensional ◽

Two Dimensional ◽

First Principles Calculations

According to first-principles calculations, it should be possible to grow two-dimensional (2D) forms of copper thio-cyanate (CuSCN) and copper seleno-cyanate (CuSeCN) since their energies are only marginally higher than those of their most stable three-dimensional (3D) wurtzite structures.

Download Full-text

Synthesis and characterization of robust three-dimensional chiral metal sulfates

RSC Advances ◽

10.1039/c4ra09471a ◽

2014 ◽

Vol 4 (92) ◽

pp. 50435-50442 ◽

Cited By ~ 7

Author(s):

J. N. Behera ◽

Joydeep Bhattacharjee ◽

Satoshi Horike ◽

Subba R. Marri ◽

Prem P. Dahiya

Keyword(s):

Thermal Decomposition ◽

High Temperature ◽

First Principles ◽

Three Dimensional ◽

Ammonium Ion ◽

Synthesis And Characterization ◽

First Principles Calculations ◽

X Ray Diffraction ◽

X Ray

Chiral three-dimensional Mg(ii) and Mn(ii) sulfates have been synthesized, well characterized and studied from first-principles calculations. High temperature X-ray diffraction, thermogravimetric analysis and DFT calculations reveal that the structures of both the compounds remain intact even after the thermal decomposition of the ammonium ion.

Download Full-text