Phonon instability. Here, the authors demonstrate .
Phonon instability The intricate renormalization of electronic states due to electron Mar 4, 2023 · We address the problem of predicting the zero-temperature dynamical stability (DS) of a periodic crystal without computing its full phonon band structure. c Transverse Peierls Jul 8, 2025 · We show that thermal equilibrium between conduction electrons and phonons becomes kinetically unstable when the renormalized electron-phonon coupling exceeds a certain threshold. Density functional theory (DFT) calculations for the re-ported room temperature crystal structure of U2Ti show an instability of a longitudinal optical phonon at (0 0 , , 1 /2) [16]. The lattice dynamics of bcc and fcc W is studied as a function of pressure using the density- functional linear-response theory. Here, we show how a subtle competition of energetic and entropic free-energy components governs its thermodynamics and the sequence of phase transitions it undergoes upon cooling. The harmonic phonon spectrum of a solid is the simplest description of its structural dynamics and can be straightforwardly derived from the Hellman–Feynman forces obtained in a ground-state electronic structure calculation. This first-principles study offers quantitative analysis to understand the atomic bonding and dynamics in phase-change materials. Yuzbashyan and 2 other authors Mar 19, 2025 · All-electrical excitation of the hyperbolic phonon polaritons in hexagonal boron nitride by drifting charge carriers in nearby graphene results in electroluminescence at mid-infrared frequencies. Apr 3, 2015 · Charge-density-wave (CDW) order has long been interpreted as arising from a Fermi-surface instability in an initiating metallic phase. Triggered ferroelectricity in HfO 2 from polar hybrid zone-boundary phonon instability Seongjoo Jung, Turan Birol∗ Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, 55455, USA ∗Corresponding author. Science [Internet]. Sep 23, 2003 · We have calculated the phonon spectra of aluminum as a function of strain using density functional perturbation theory for $ 110 $, $ 100 $, and $ 111 $ uniaxial tension, as well as relaxed $ 112 {111}$ shear. Santos1 arXiv:0807. We discuss a splitting of the Dirac points that leads to phonon bands with nonzero Chern Aug 24, 2012 · Meanwhile, dynamic instability of a crystal lattice has been studied via separate calculations of the phonon spectra of the crystal lattice at each step along every deformation pathway. The energy of the crystal structure is minimized by dimeriza-tion of uranium sites along the hexagonal c axis. Using density functional theory, we reveal the mechanisms of mechanical failure of pure graphene under a generic state of tension at zero temperature. May 30, 2018 · The evolution of atomic structure in phase-change materials is an essential ingredient for designing next-generation nonvolatile memory devices and memristors, yet has remained elusive for decades. Oct 13, 2020 · Bare electron susceptibility, phonon linewidth, and electron-phonon coupling calculations suggest that the CDW instability is driven by softened phonon modes due to the strong electron-phonon coupling interactions. ” Nature Physics, Springer Science and Business Media LLC, 2020. Insert shows the linear regression of the initial stress strain curves for obtaining the corresponding elastic moduli. Electron-phonon instability in graphene revealed by global and local noise probes Publication information: Andersen TI, Dwyer BL, Sanchez-Yamagishi JD, Rodriguez-Nieva JF, Agarwal K, Watanabe K, Taniguchi T, Demler EA, Kim P, Park H, Lukin MD. May 30, 2023 · Amid phonon instability, essential variations in the Gr\"ueisen parameter and participation ratio are observed, signifying the correlation between vibrational and configurational space in such compositional complex alloys. The article has been published as: The phonon instability and thermal equation of state of Mo are extensively investigated using density functional theory. b The LA Kohn anomaly induced by the classical Peierls transition. 5–7,14 The Ni- derived acoustic phonon modes due to their likely link with the superconducting transition 21 and instability of the acoustic phonon modes at some points in Brillouin zone are of special interest. At 0 K, phonon instability controls the ideal strength and the ultrafast dynamics of defect nucleation in perfect crystals under high stress. TABLE I. The results show that failure mechanisms of silicene under armchair and zigzag uniaxial tensions are elastic instability (phonon instability occurs behind the elastic instability). We have calculated the phonon spectra of graphene as a function of uniaxial tension by density functional perturbation theory to assess the first occurrence of phonon instability on the strain path, which controls the Dec 7, 2009 · Microtubules (MTs) are self-assembled hollow protein tubes playing important functions in live cells. The dispersion of this stacking configuration is relatively insensitive to bias and does not change significantly in response to an applied field. Jun 1, 2020 · Request PDF | Magnetically driven phonon instability enables the metal–insulator transition in h-FeS | Hexagonal iron sulfide exhibits a fascinating coexistence of metal–insulator, structural Oct 15, 2015 · Investigating the lattice instability by obtaining the phonon dispersion in whole Brillouin zone from first-principles. Phonon instability in two-dimensional dipolar Bose-Einstein Condensates R. The largest instability of Jan 28, 2022 · Strong phonon anomalies are prominent not only below the density-wave transition, but also at high temperatures, suggesting an intricate interplay of phonons with the underlying electronic structure. Summary of the ideal tensile strengths, critical strains, and failure mechanisms of monolayer borophene under three strain paths and comparison with graphene, silicene and BP. 2, D-30167, Hannover, Germany 2 Laboratoire de Physique Théorique de la Matière Condensée, Université Pierre at Marie Curie, case courier 121, 4 place Aug 28, 2007 · We have calculated the phonon spectra of graphene as a function of uniaxial tension by density functional perturbation theory to assess the first occurrence of phonon instability on the strain Oct 30, 2024 · An alternative route to drive the transverse optical phonon softening sheds light on developing a unified theory for ferroelectricity enhancement in ultrathin films free from depolarization fields Jun 1, 2025 · Title: Instability of metals with respect to strong electron-phonon interaction Abstract: Using standard kinetic equations, we show that the thermal equilibrium between conduction electrons and phonons is unstable when the renormalized electron-phonon coupling exceeds a certain threshold. No anomalies are observed in the Born effective charges [17–19], and depolarization field does not effectively suppress the polarization [2,3,20]. 37, on the other hand, focused only on the low-T antiferromagnetic transition (~75 K), leaving open questions about the mechanism of the phonon Apr 12, 2019 · Our observations, including the dependence on density and temperature, are consistently explained by the emergence of an electron-phonon Cerenkov instability at supersonic drift velocities. Our calculations revealed an instability in the hexagonal structure of U 2Ti which is not observed in the earlier studies on this system. Pris- Jan 5, 2018 · Phonon dispersion, structural distortion and the elastic properties of U2 Ti are studied using ab-initio techniques. As a result, a transient gas of attractive solitons is formed, and collapse may We identify no specific strongly coupled phonon modes in TiSe 2 (38) from the perspective of electron-phonon energy transfer (or lattice heating), indicating that a highly anisotropic χ (q) and its dependence on carrier concentration is the primary driver of the phonon softening and lattice instability in TiSe 2. Their building block is a protein called tubulin, which self-assembles in a particulate 2 dimensional lattice. The elements exhibit similar phonon instabilities which cover large parts of the Brillouin zone. We study the vibrational modes of this lattice and find Dirac points in the phonon spectrum. Dec 29, 2023 · In BECs with attractive s-wave collision interaction, the phonon excitation can lead to a phonon instability [1,2]. Feb 8, 2016 · Inelastic neutron scattering was used to measure the phonon density of states in Cu12Sb4S13 and Cu10Zn2Sb4S13, both of which possess a localized, low-energy phonon mode associated with strongly anharmonic copper displacements that suppress κ. The calculated phonon dispersion curves agree well with experiments. Feb 2, 2009 · The partially attractive character of the dipole-dipole interaction leads to phonon instability in dipolar Bose-Einstein condensates, which is followed by collapse in 3D geometries. Feb 28, 2023 · In this paper, employing density functional theory, many-body dynamic mean field theory, and determinant quantum Monte Carlo calculations, we propose a synergetic contribution from both electronic instability (EI) and moment-dependent electron-phonon coupling (MEPC). B 76, 064120 (2007) - Published 28 August, 2007 Ideal strength, the maximum stress an in nite, defect-free crystal can withstand at zero temperature, is an upper limit that provides a measure for the intrinsic strength of the chemical bonding and overall stability of a material [1]. (2007) Ab Initio Calculation of Ideal Strength and Phonon Instability of Graphene under Tension. Jul 20, 2022 · The lattice vibrations (phonon modes) of crystals underpin a large number of material properties. At the initial stage, the maxon instability leads to the formation of a supersolid-like stripe pattern, but after a long time of evolution, the non-Hermitian nature of the system destroys this stripe pattern. We show that under such conditions the electric current produces a phonon instability: populations of phonon modes propagating almost collinearly with the superlattice axis increase exponentially in time. Aug 7, 2020 · The calculated phonon dispersions show two unstable optical branches. The appearance of imaginary frequencies in the phonon spectra indicates the beginning of the dynamic instability of the crystal lattice12–15. In particular, the entire T[11 ̄0]@jj 0 branch, where the zone-boundary phonon is responsible In this paper, the energy of the Bain path in Al and the instability of phonons during uniaxial compression deformation along <001> are studied ab initio. Deformation causes shifts along the {111} planes of the initial Ideal strength, the maximum stress an in nite, defect-free crystal can withstand at zero temperature, is an upper limit that provides a measure for the intrinsic strength of the chemical bonding and overall stability of a material [1]. other] 23 Jul 2008 1 Institut für Theoretische Physik , Leibniz Universität Hannover, Appelstr. First, we summarize the evolution of lattice and Graphene-based sp2-carbon nanostructures such as carbon nanotubes and nanofibers can fail near their ideal strengths due to their exceedingly small dimensions. Feb 15, 2023 · The role of phonon anharmonicity on the structural stability and phonon heat transport of CrFeCoNiCux high-entropy alloys at finite temperatures Nov 26, 2024 · Electron-boson interactions in the weak itinerant ferromagnet LaCo2P2 are investigated, addressing both surface and bulk properties. This roton minimum can lead to a stable supersolid if G = 0. Here we demonstrate phonon properties Mar 1, 2016 · However, the Peierls instability remains present whatever the value of the electron–phonon coupling [29], showing the generality of the Peierls' result. Jun 4, 2012 · It is identified that the tensile strength of single-layer MoS 2 are dictated by out-of-plane soft-mode phonon instability under biaxial tension and uniaxial tension along the armchair direction. As a consequence, a transient gas Nov 16, 2016 · result of pressure-induced instability of a phonon mode that relates to the rotation of the oxygen octahedra. We prove that negative electronic specific heat, ${C}_{\\mathrm{el}}<0$, is sufficient to trigger the instability. Experimental the evidences for CDW phases transitions is explained using an excitonic mechanism without Femi surface nesting and Jahn-Teller distortion [31]. May 31, 2023 · The phonon instability criterion also sets up the ideal strength and ideal strain of a crystal [37,38]. This phonon mode shows an increasing softening with pressure, ultimately lea ng to an isostructural phase transition characterized by the degree of the rotation of the oxygen octahedra. The solid and dash arrows indicate the onset strains for phonon instability and elastic instability, respectively. Here, the authors demonstrate Apr 25, 2023 · The phonon splitting and instability strongly depend on the laser intensity, frequency, chemical potential, and temperature of photoexcited electrons. In principle, while phonon scattering loss is typically irreversible, long-lived phonons can act as a dominant source of instability within the experimental setup. We have calculated the phonon spectra of graphene as a function of uniaxial tension by density functional perturbation theory to assess the first occurrence of phonon instability on the strain path, which controls the strength of a Dec 29, 2023 · In the case of the phonon-maxon-roton excitation spectrum, maxon instability, rather than the usual roton instability, could be induced. In one-dimensional systems, the Mar 1, 2021 · This phonon instability q cdw = π a (1 2, 0, 0), at M is a Kohn instability, corresponding to the CDW phase translating to a stle 2 × 2 supercell in real space [21, 29, 30]. and Li, J. Feb 23, 2024 · The mechanism of charge density wave order in V-based kagome metals has been debated. It is identified that the tensile strength of single-layer MoS 2 are dictated by out-of-plane soft-mode phonon instability under biaxial tension and uniaxial tension along the armchair direction. By means of Nov 1, 2015 · Phonon plays essential roles in dynamical behaviors and thermal properties, which are central topics in fundamental issues of materials science. The article has been published as: Jan 13, 2025 · In this study, we investigate the strain-induced phase transition in ML $ {\mathrm {IrTe}}_ {2}$ using first-principles calculations and constrained density-functional perturbation theory. A key This structural transition coincides with a recently-reported metal-insulator transition, and the structural instability is related to the very low thermal conductivity κ in these materials. However, even after the Nov 16, 2016 · This phonon mode shows an increasing softening with pressure, ultimately leading to an isostructural phase transition characterized by the degree of the rotation of the oxygen octahedra. Mar 31, 2008 · The second phase transition is associated with the instability of a low wave number mode, which behaves as soft mode. We find that the soft phonons associated with structural instability are hardened by biaxial tensile strain and that the trigonal phase is stabilized. At high pressures andT› 0 K, bcc W has a higher enthalpy than the fcc and hcp phases and it develops phonon softening anomalies related to this thermodynamic instability; however, it remains dynamically stable. However, how a soft phonon evolves into a lattice The problem of phonon instability of an electron-phonon system is studied. Specifically, the instability sets in as soon as the quasiparticle weight becomes negative over a Jul 31, 2015 · The phonon instability in a homogeneous two-dimensional condensate of tilted dipoles always features a transient stripe pattern, which eventually breaks into a metastable soliton gas. nderstanding the interplay of the spin, phonon and charge degrees of freedom is critical to rationalize and control metal-insulator transitions (MITs) and magnetoelectric materials. Jun 1, 2020 · Hexagonal iron sulfide exhibits a fascinating coexistence of metal–insulator, structural and magnetic transitions, reflecting an intimate interplay of its spin, phonon and charge degrees of freedom. Abstract Phonon plays essential roles in dynamical behaviors and thermal properties, which are central topics in fundamental issues of materials science. Apr 13, 2020 · The magnetically driven phonon instability occurring at high temperature is a promising general mechanism for the design of new multiferroics. When the electrons have a net drift velocity relative to the lattice in the presence of a static, uniform magnetic field, it is found that the phonons may become unstable when certain threshold values for the drift velocity and the magnetic field are exceeded. These results offer the opportunity for tunable terahertz generation and active phononic devices based on two-dimensional materials. Marianetti PDF The q-resolved INS measurements of Petit et al. Jul 24, 2024 · Such an apparent temperature-dependent softening probably originates from the nesting acoustic-optical mode contribution of LEB and substantiates the phonon instability, which would further May 2, 2012 · A number of model and first principles investigations of lattice dynamics of MgCNi 3 have been performed. Hexagonal iron sulfide exhibits a fascinating coexistence of metal-insulator, structural and magnetic transitions, reflecting an intimate interplay of its spin, phonon and charge degrees of freedom Aug 28, 2007 · We have calculated the phonon spectra of graphene as a function of uniaxial tension by density functional perturbation theory to assess the first occurrence of phonon instability on the strain path, which controls the strength of a defect-free crystal at $0\phantom {\rule {0. This is more or less expected. The calculated phonon dispersions show two unstable optical branches. Kysar Chris A. Feb 15, 2024 · We demonstrate the potential of our method for engineering phonon band structure, phonon density of states (DOS), and thermal transport properties. 3 (a)- (b). Their importance stems from the fact that in some cases, like continuous structural phase transitions in crystalline solids, soft phonon modes signal an incoming instability that drives the system from one crystal structure to another. In contrast, the widely unstable shear modes of fcc W May 30, 2023 · The results of unusual phonon features could give insight into how the structure, elasticity, and plasticity interact in generic multi-component high-entropy alloys. Cooper and Jeffrey W. Phonopy is an open source code for such calculations launched by the present authors, which has been world-widely used. Structure instability of a lattice arises in the sold called Peirers distortion, particularly for 1D crystals, and is due mainly to disorder when there is a transition from metal to an insulator. Dec 1, 2009 · Phonon instability and self-organized structures in multilayer stacks of confined dipolar Bose-Einstein condensates in optical lattices Jun 7, 2015 · The phonon-instability in a homogeneous 2D condensate of tilted dipoles always features a transient stripe pattern, which eventually breaks into a metastable soliton gas. Dec 1, 2014 · Phonon calculations have demonstrated that failure mechanisms of silicene under uniaxial tensions are elastic instability (phonon instability occurs behind the elastic instability). Rev. Jan 5, 2018 · This instability is demonstrated through the imaginary phonon frequencies found around the A-point in the Brillouin zone. Besides Dec 1, 2014 · This instability determines the strength of graphene since it occurs prior to the elastic failure. 4 2when the phonon dispersion is evaluated at the static total-energy minimum geometry; however, the unstable phonon branch becomes stable when the zero-point energy and the associ- ated lattice expansion are considered within the quasihar- monic approximation. The partially attractive character of the dipole-dipole interaction leads to phonon instability in dipolar condensates, which is followed by collapse in three-dimensional geometries. 3683v1 [cond-mat. Note that quantum fluctuations have more drastic effect on the Peierls instability in a spin-less electron gas [28], [29] and by consequence on the SP instability. Apr 13, 2020 · A detailed and systematic X-ray and neutron scattering study of hexagonal iron sulfide uncovers the critical role of spin-phonon coupling in promoting the metal-insulator transition in this system. Jan 2, 2018 · Yet, the proposed instability of a zone-boundary phonon mode, driving the emergence of ferroelectricity via coupling to a polar mode, remains to be directly observed. While phonon-electron coupling has been recently suggested to influence the formation of CDW order in quasi-two-dimensional (quasi-2D) systems, the presumed dominant importance of Fermi-surface nesting remains largely unquestioned in quasi-1D systems. Jun 1, 2025 · Roton instability is characterized by a pronounced dip in the excitation spectrum at the phonon energy level with infinitesimal G ≠ 0. Graphene-based sp<SUP>2</SUP> -carbon nanostructures such as carbon nanotubes and nanofibers can fail near their ideal strengths due to their exceedingly small dimensions. 15 hours ago · The interaction between a LA phonon and isotropic s -orbital conduction electrons yields a CDW instability. Nov 15, 2023 · Soft phonon modes are the normal modes at finite wavevectors, whose frequency approaches zero as an effect of varying some parameter of the system. Dec 1, 2014 · The phonon dispersions of silicene under three types of tensions are calculated using the finite differences method to examine stability conditions. The importance of first principles phonon calculations cannot be overly emphasized. Pedri2 and L. This instability is demonstrated through the imaginary phonon frequencies found around the A-point in the Brillouin zone. Here we demonstrate phonon properties with The results bring out the anomalous vibrational mode instability in the phonon dispersion curves and phonon density of states of MgCNi3. Electron-phonon instability in graphene revealed by global and local noise probes. We also find that this phase transition is accompanied by an anisotropic compression, in excellent agreement with experiments. As a result, a transient gas of attractive solitons is formed, and collapse may 19 The model also predicts that the electron-phonon Cerenkov instability gives rise to a con-of forward-moving acoustic phonon modes exper-iences a faster rate of stimulated emission ðgem q Þ than absorption ðgabs ( ). c Transverse Peierls Jul 20, 2022 · The lattice vibrations (phonon modes) of crystals underpin a large number of material properties. Dec 1, 2023 · This enables to verify the presence of a phonon softening, which is predicted theoretically to occur above T CDW, to assist the CDW instability. For the emitted q Þ 11–14 phononstoamplify,gem mustexceed thelossrate q due to absorption and other decay sources. “ Magnetically driven phonon instability enables the metal–insulator transition in h-FeS. Nath1 , P. In all four cases, phonon instabilities occur at points away from the center of the Brillouin zone and intrude before the material becomes unstable according to elastic stability Sep 17, 2024 · Here, we carry out a high-throughput first-principles study of the kagome 1:6:6 family MT _6 Z _6 materials in space group 191, focusing on their phonon instability and electronic flat bands. of 330 70 GPa for MoS2 nanosheets consisted of 5 to ± 25 layers. In particular, the entire T[11 ̄0]@jj 0 branch, where the zone-boundary phonon is responsible Bansal, Dipanshu, et al. However, it is difficult to realize the electronic stabilities in practice, due to increased phonon scattering at high drift velocities. Apr 3, 2001 · These results suggest that a polar optical phonon instability occurs in GaAs and that this instability is responsible for the onset of intervalley transitions. The calculated phonon dispersion curves and phonon density of states are in good agreement with the measured and density functional theoretical DFT data. In this work we present a direct observation of the phonon softening and T CDW determination in LaPt 2 Si 2, measured with inelastic neutron scattering (INS). However, how a soft phonon evolves into a lattice defect is still unclear. Jan 30, 2002 · An electric current occurs due to the phonon-induced interwell hops. Although phonon scattering is typically an irreversible loss channel, long-lived phonons can themselves act as a source of instabilities. May 30, 2023 · Here we develop a set of computational metrics to characterize the features of phonons and the instability pathway in a prototypical ternary CoCrNi MPEA by atomistic simulations. Apr 14, 2020 · Magnetically driven phonon instability enables the metal–insulator transition in h-FeS These results reveal the importance of spin–phonon coupling to tune anharmonic effects, and the role of phonon instabilities in opening up the band gap across the metal-insulator transition. Jan 8, 2025 · Employing a high-throughput screening methodology to scrutinize zone-center electron-phonon couplings, we found an inverse relationship between thermodynamic stability and electron-phonon coupling strength in the resulting ternary metal borides. Nov 27, 2020 · To what extent the charge carriers can alter phonon heat conduction at environmental temperatures through electron–phonon interactions is an open question. B. When the flat bands are located away from the Fermi level, we find a large number of phonon instabilities, which can be classified into three types, based on the phonon dispersion and vibrational modes. For the type-I phonon instability in the NiSi/Ge-166 family, the collection of their imaginary frequency and IRREPs at low-T is shown in Fig. Several other factors also support this theory. All the acoustic branches are stable, which shows that an elastic instability is not the primary cause of the experimentally observed orthorhombic-to-monoclinic structural transition in this material. The discovery of the soft mode in $ {\mathrm {Bi}}_ {2}\mathrm {W} {\mathrm {O}}_ {6}$ that corresponds most likely to the $ {E}_ {u}$ mode responsible for ferroelectricity in Aurivillius family of compounds proves that this Nov 16, 2016 · This phonon mode shows an increasing softening with pressure, ultimately leading to an isostructural phase transition characterized by the degree of the rotation of the oxygen octahedra. The symmetry analysis reveals similar IRREPs for their leading instabilities governed by kagome nets. We show that the nature of this instability is fundamentally different in two-dimensional condensates, due to the dipole-induced stabilization of two-dimensional bright solitons. Apr 12, 2019 · Electron-phonon instability in graphene revealed by global and local noise probes Understanding and controlling nonequilibrium electronic phenomena is an outstanding challenge in science and engineering. , Ming, P. Apr 12, 2019 · In practice, such electronic instabilities are difficult to realize owing to increased phonon scattering at high drift velocities. 3em} {0ex}}\mathrm {K}$. Also, out-of-plane Liu, F. All previous theoretical calculations including our own model calculation 7 Sep 29, 2024 · View a PDF of the paper titled Instability of metals with respect to strong electron-phonon interaction, by Emil A. This instability Aug 7, 2020 · The calculated phonon dispersions show two unstable optical branches. Ideal strength is ultimately dictated by what is known as the elastic instability, whereby a crystal becomes unstable with respect to a homogeneous deformation Dec 10, 2010 · Recent experiments established pure graphene as the strongest material known to mankind, further invigorating the question of how graphene fails. Therefore both the necessary and sufficient condition for mechanical instability of a crystal at low Jan 1, 2020 · The phonon dispersion of the AA system shows degenerate imaginary modes at the point, indicating the presence of a phonon instability. Metal-insulator transitions can be driven by structural distortions, May 25, 2012 · This instability of phonon mode could be a precursor leading to the dynamic disorder of the lithium sublattice. One failure mechanism is a novel soft-mode phonon instability of the ${K}_{1}$ mode, whereby the The lattice dynamics of the elements Sc, Ti, La, and Hf in the bcc structure is studied using the density-functional linear-response theory. Feb 23, 2023 · The mechanism of the charge density wave in kagome metals is under intense debate. The partially attractive character of the dipole-dipole interaction leads to phonon instability in dipolar Bose-Einstein condensates, which is followed by collapse in 3D geometries. Similar results are observed for the case of wurtzite GaN at T =300 K, as is seen in Fig. We perform an energy decomposition that demonstrates why the soft modes at the K point are unique and how strain drives the phonon instability. 19 The model also predicts that the electron-phonon Cerenkov instability gives rise to a con-of forward-moving acoustic phonon modes exper-iences a faster rate of stimulated emission ðgem q Þ than absorption ðgabs ( ). We have calculated the phonon spectra of graphene as a function of uniaxial tension by density functional perturbation theory to assess the first occurrence of phonon instability on the strain path, which controls the strength of a Oct 30, 2014 · Comment on “Ideal strength and phonon instability in single-layer 𝐌 𝐨 𝐒 2 ” Ryan C. Here, by using a combination of diffuse scattering and inelastic x-ray scattering, the authors show that the . Apr 1, 2020 · I study dynamical instabilities in Ta2NiSe5 using density functional theory based calculations. Reply to “Comment on ‘Ideal strength and phonon instability in single-layer MoS {2}’ ” This is the accepted manuscript made available via CHORUS. Feb 8, 2016 · Structural phase transition and phonon instability in Cu {12}Sb {4}S {13} This is the accepted manuscript made available via CHORUS. Such kind of instability may also happen for graphene under inequibiaxial strain as long as the point-like Fermi-surface is retained because a phonon wave vector q → that connects two Dirac points still exists. 3b. Mar 24, 2003 · The instability is observed when the electron drift velocity is larger than the phase velocity of optical phonons and rather resembles a “sonic boom” for optical phonons. This instability leads to a Peierl's type of dimerization of U atoms along Z direction which will result in the formation of charge density wave (CDW) in the system. Phonon softening initiates the dynamic instability, which triggers Apr 13, 2020 · A detailed and systematic X-ray and neutron scattering study of hexagonal iron sulfide uncovers the critical role of spin-phonon coupling in promoting the metal-insulator transition in this system. CDW order can be suppressed by pressure, concomitant with the appearance of the superconductivity. This study motivates future experimental investigation of the optical fine tuning and regulation of shear phonons and layer stacking order in layered van der Waals materials. Here, we develop a full-Brillouin zone soft-phonon-searching algorithm that shows outstanding accuracy and efficiency for pinpointing general phonon instability within the joint omposed into phonon modes, which are nearly independent of each other (normal modes). Empirical potential model calculations were carried out to deduce the probable direction of vacancy-assisted lithium movement by constructing a supercell consisting of 12 000 atoms. Hexagonal iron sulfide exhibits a fascinating coexistence of metal-insulator, structural and magnetic transitions, reflecting an intimate interplay of its spin, phonon and charge degrees of freedom Aug 15, 2016 · Ab initio calculation of ideal strength and phonon instability of graphene under tension Fang Liu, Pingbing Ming, and Ju Li Phys. It is shown that, at a strain of about 15%, dynamic loss of structure stability is observed due to short-wavelength phonons, which thus determine the theoretical strength of Al. In this paper, employing density functional theory, many-body dynamic mean field theory, and determinant quantum Monte Carlo calculations, we propose a synergetic contribution from both electronic instability (EI) and moment-dependent electron-phonon coupling (MEPC). Here the authors use a range of experimental techniques combined with ab initio calculations to study the Graphene-based sp2-carbon nanostructures such as carbon nanotubes and nanofibers can fail near their ideal strengths due to their exceedingly small dimensions. failure mechanism is phonon instability and such an instability is dictated by out-of-plane acoustical (ZA) mode. Physical Review B, 76, 064120. Pris- The absence of a polar structural instability, specifically the Γ−4 mode, suggests that the ferroelectricity in fluorite HfO2 (Fm ̄3m, #225) is improper in nature [4]. The presence of imaginary harmonic modes in the spectrum indicates that Mar 13, 2009 · This phonon branch is very sensitive to the lattice parameters and can be stabilized by including lattice expansion due to zero-point vibrational contributions in the quasiharmonic approximation. We show that in 2D, the nature of the post-instability dynamics is fundamentally different, due to the stabilization of 2D solitons. fsrwo gghtbz ljmmlw meman fnp pohwcnw sdswi uznri llyp ajrl unoxu ged wtrionn ntq ywlv