<i>Ab initio</i>calculation of phonon dispersions in semiconductors

Giannozzi, Paolo; Gironcoli, Stefano de; Pavone, P.; Baroni, Stefano

doi:10.1103/physrevb.43.7231

Cited by 1,728 publications

(957 citation statements)

References 26 publications

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“…Our results for Si and C agree well with experiment [36] and other theoretical [37,38] results. Note that we have no experimental data to compare with our results for Si 1−x C x alloys.…”

Section: Phonons Dispersionsupporting

confidence: 91%

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Langueur

Kassali

2017

Int J Thermophys

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Using a density functional scheme, for the first time the carbon dependence on the structural, dynamic, thermodynamic, and dynamic properties of Si 1−x C x alloys (x = 0.0 to 1.0 in steps of 0.125) has been investigated. The structural properties of these materials, in particular, the composition dependence of the lattice parameter and bulk modulus, are in excellent agreement with experimental data and follow a quadratic law in (x). A nonlinear relationship is found between the elastic constants C 11 , C 12 , and C 44 and the carbon concentration (x). The behavior of the acoustical and optical phonon frequencies at high-symmetry points Γ , X , and L is predicted. Through the quasi-harmonic Debye model, in which the photonic effects are taken into account, the Debye temperature, the heat capacity, the Helmholtz free energy, the internal energy, and the entropy are determined for the Si 1−x C x compounds.

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“…Our results for Si and C agree well with experiment [36] and other theoretical [37,38] results. Note that we have no experimental data to compare with our results for Si 1−x C x alloys.…”

Section: Phonons Dispersionsupporting

confidence: 91%

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Langueur

Kassali

2017

Int J Thermophys

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“…The Born effective charges describe the atomic response to such a field and this leads to an additional restoring force on the atoms and an increase in energy cost for the displacement pattern of the LO mode with respect to the TO mode. The resulting relationship between the square of the frequencies of these modes is well-known in 3D bulk materials 10,11,13 . As the central analytical result of this paper, we generalize this relationship for both 2D and 3D layered materials as…”

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confidence: 84%

Breakdown of Optical Phonons’ Splitting in Two-Dimensional Materials

et al. 2017

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We investigate the long-wavelength dispersion of longitudinal and transverse optical phonon modes in polar two-dimensional materials, multilayers, and their heterostructures. Using analytical models and density-functional perturbation theory in a two-dimensional framework, we show that, at variance with the three-dimensional case, these modes are degenerate at the zone center but the macroscopic electric field associated with the longitudinal-optical modes gives rise to a finite slope at the zone center in their corresponding phonon dispersions. This slope increases linearly with the number of layers and it is determined solely by the Born effective charges of the material and the dielectric properties of the surrounding media. Screening from the environment can greatly reduce the slope splitting between the longitudinal and transverse optical modes and can be seen in the experimentally relevant case of boron nitride-graphene heterostructures. As the phonon momentum increases, the intrinsic screening properties of the two-dimensional material dictate the transition to a momentum-independent splitting similar to that of three-dimensional materials. These considerations are essential to understand electrical transport and optical coupling in two-dimensional systems.PACS numbers: 77.22.Ej Van der Waals heterostructures 1 will assuredly play a key role in future electronic and optoelectronic devices 2-5 . Many of the potential candidates to build those next-generation devices are polar two-dimensional (2D) materials, including transition-metal dichalcogenides (TMDs) and hexagonal boron nitride (h-BN). A significant consequence of polarity in these materials is the generation of long-ranged electric fields by the polarization density associated with their longitudinal optical (LO) phonon modes. These fields strongly influence the transport properties of the monolayers as well as their heterostructures, via the Fröhlich electron-phonon interaction 6-8 . Importantly, they lead to additional dipoledipole interaction terms affecting the dispersion characteristics of optical phonons. This leads to a splitting between the LO and transverse optical (TO) modes, driven by the long-ranged Coulomb interactions and electronic screening. Here, we show in detail how this LO-TO splitting is drastically affected by dimensionality. In 3D, it is well understood how this splitting is independent of the norm of the phonon momentum and how it lifts the degeneracy of the LO and TO phonon modes in the long wavelength limit. We show here that in 2D, the splitting depends on the norm of the phonon momentum, vanishes at the zone center and leads to a discontinuity in the derivative of the LO phonon dispersion. First-principles computations of this phenomenon are delicate independently of dimensionality, due to the long-ranged nature of the dipole-dipole interactions leading to electric fields that are not compatible with periodic boundary conditions. In 3D materials, however, the development of analytical models based on the Born effectiv...

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“…To perform the integration over the Brillouin zone the 12x12x12 Monkhorst-Pack k-point grid was used [17]. Phonon spectra calculations were carried out using fast Fourier transformation of real-space interatomic force constants matrix obtained via dynamic matrices calculated for the 4x4x4 q-point grid [18]. In our work we considered the vacancy ordered phase Pd 3 VacH 4 (Cu 3 Au-type structure) with hydrogen atoms occupying either four tetrahedral or four octahedral sites.…”

Section: Calculation Detailsmentioning

confidence: 99%

Dynamic stability of palladium hydride: An ab initio study

Isaeva

Бажанов

Isaev

et al. 2011

International Journal of Hydrogen Energy

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We present results of our ab initio studies of electronic and dynamic properties of ideal palladium hydride PdH and its vacancy ordered defect phase Pd 3 VacH 4 with L1 2 crystal structure proposed theoretically and found experimentally. Quantum and electronic properties of these hydrides, such as phonon dispersion relations and the vacancy formation enthalpies have been studied. Dynamic stability of the defect phase Pd 3 VacH 4 with respect to different site occupation of hydrogen atoms at the equilibrium state and under pressure was analyzed. It was shown that positions of hydrogen atoms in the defect phase strongly affect its stability and may be a reason for further phase transitions in the defect phase.

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Ab initiocalculation of phonon dispersions in semiconductors

Cited by 1,728 publications

References 26 publications

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

Breakdown of Optical Phonons’ Splitting in Two-Dimensional Materials

Dynamic stability of palladium hydride: An ab initio study

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