Assessment of discrete breathers in the metallic hydrides

Dubinko, V.I.; Laptev, Denis V.; Terentyev, D.; Irwin, Klee

doi:10.1016/j.commatsci.2018.11.007

Cited by 17 publications

(6 citation statements)

References 64 publications

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“…From this observation it follows that the heat capacity of the crystals having a gap in the phonon spectrum and supporting soft-type anharmonicity DBs (e.g., NaI [31,32,[38][39][40], ordered alloys [51][52][53][54], and graphane [37]) should increase due to the excitation of DBs. For the crystals without a gap in the phonon spectrum (e.g., pure metals [45][46][47][48][49][50] and covalent crystals [43,44]) only hard-type anharmonicity DBs can exist and their excitation will reduce heat capacity.…”

Section: Discussionmentioning

confidence: 91%

“…[39,40]. Using molecular dynamics, DBs have been found in monoatomic Morse crystals [41,42], covalent crystals Si, Ge and diamond [43,44], pure metals [45][46][47][48][49][50], ordered alloys [51][52][53][54], carbon and hydrocarbon nanomaterials [55][56][57][58][59][60][61][62][63][64][65][66][67], boron nitride [68], and proteins [69][70][71][72]. Essential limitation of any MD model is the choice of the interatomic potentials which largely determine the reliability of the obtained results [66].…”

Section: Introductionmentioning

confidence: 99%

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Effect of discrete breathers on the specific heat of a nonlinear chain

Singh,

Morkina,

Korznikova

et al. 2019

Preprint

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Defect-free crystal lattices can accommodate spatially localized, high amplitude atomic vibrations called either discrete breathers (DBs) or intrinsic localized modes (ILMs). This has been explored by a number of molecular dynamics studies and, in few cases, by the first-principles calculations. A number of experimental measurements of crystal vibrational spectra was performed aiming to prove the existence of DBs in thermal equilibrium at elevated temperature. However, the interpretation of these experimental results is still debated. Direct high-resolution imaging of DBs in crystals is hardly possible due to their nanometer size and short lifetime. An alternative way to substantiate the existence of DBs is to evaluate their impact on the measurable macroscopic properties of crystals and validate such prediction. One of such properties is specific heat. In fact, the measurements of heat capacity was done for alpha-uranium by Manley and co-workers in conditions where the presence of DBs was expected. In the present study, employing a one-dimensional nonlinear lattice with an on-site potential, we analyze the effect of DBs on its specific heat. In the most transparent way, this can be done by monitoring the chain temperature in a non-equilibrium process, at the emergence of modulational instability, with total energy of the chain being conserved. For the onsite potential of hard-type (soft-type) anharmonicity, the instability of q = π mode (q = 0 mode) results in the appearance of long-living DBs that gradually dissipate their energy and eventually the system approaches thermal equilibrium with spatially uniform and temporally constant temperature. The variation of specific heat at constant volume is evaluated during this relaxation process. It is concluded that DBs affect specific heat of the nonlinear chain and for the case of hard-type (softtype) anharmonicity they reduce (increase) the specific heat.

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Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Effect of discrete breathers on the specific heat of a nonlinear chain

Singh,

Morkina,

Korznikova

et al. 2019

Preprint

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“…A similar formulation arises in problems when a perturbation is a trajectory of a onedimensional or two-dimensional process that modulates the potential change during the motion of a particle. A similar situation is realized, in particular, when an electron moves along the crystalline axis [1,2]. In this case, the role of time in the problem is played by the depth of particle penetration, and the function of perturbation, describes the forced oscillations of the crystal lattice.…”

Section: Introductionmentioning

confidence: 89%

“…In NSC KIPT, work is underway to investigate the influence of various types of irradiation on the properties of condensed media. The mechanism of changing the properties of materials during irradiation is associated with the excitation of nonlinear localized oscillations in the lattice [1,2]. These oscillations in turn affect the dynamics of particles in it.…”

Section: Introductionmentioning

confidence: 99%

Resonant Spread Wave Function in Parabolic Potential

Mazmanishvili¹

2019

Problems of Atomic Science and Technology

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In this paper, we consider the parabolic potential, which as a whole is subject to dipole or quadrupole action (parametric resonance), which periodically changes with time, and the dynamics of the wave function of a particle. Based on the solutions found for the nonstationary Schrödinger equation, algorithms for calculating the dynamics of the wave function are constructed. The evolution of the wave function of a particle is analyzed. Asymptotic solutions of the equation of motion are given, using which the main characteristics of the wave packet are obtained. For selected types of potential perturbations, examples of the evolution of the wave function are given.

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“…Using ab initio simulations, the presence of DBs in strained graphene and graphane has been confirmed [36,37]. With the help of molecular dynamics method DBs have been studied in the ionic crystals [38][39][40], lattices with pair-wise potentials [41,42], crystals with covalent bonding [43,44], metals [45][46][47][48][49][50][51], intermetallic compounds [52][53][54][55], carbon and hydrocarbon nanomaterials [56][57][58][59][60][61][62][63][64][65][66][67][68], h-BN [69], and DNA [70][71][72][73].…”

Section: Introductionmentioning

confidence: 97%

Effect of discrete breathers on macroscopic properties of the Fermi-Pasta-Ulam chain

Korznikova,

Morkina,

Singh

et al. 2019

Preprint

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For a number of crystals the existence of spatially localized nonlinear vibrational modes, called discrete breathers (DBs), has been demonstrated using molecular dynamics and in a few cases the first-principle simulations. High-resolution imaging of DBs is a challenging task due to their relatively short lifetime ranging typically from 10 to 10 3 atomic oscillation periods (1 to 100 ps). Another way to prove that DBs exist consists in evaluation of their effect on macroscopic properties of crystals. In this paper, we study the effect of DBs on macroscopic properties of the Fermi-Pasta-Ulam chain with symmetric and asymmetric potentials. The specific heat, thermal expansion (stress), and Young's modulus are monitored during the development of modulational instability of the zone boundary mode. The instability results in the formation of chaotic DBs followed by the transition to thermal equilibrium when DBs disappear due to energy radiation in the form of small-amplitude phonons. Time evolution of the macroscopic properties during this transition is monitored. It is found that DBs reduce the specific heat for all the considered chain parameters. They increase the thermal expansion when the potential is asymmetric and, as expected, thermal expansion is not observed in the case of symmetric potential. The Young's modulus in the presence of DBs is smaller than in thermal equilibrium for the symmetric potential and for the potential with a small asymmetry, but it is larger than in thermal equilibrium for the potential with greater asymmetry.

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Assessment of discrete breathers in the metallic hydrides

Cited by 17 publications

References 64 publications

Effect of discrete breathers on the specific heat of a nonlinear chain

Effect of discrete breathers on the specific heat of a nonlinear chain

Resonant Spread Wave Function in Parabolic Potential

Effect of discrete breathers on macroscopic properties of the Fermi-Pasta-Ulam chain

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