Surface phonon dispersion curves of graphite (0001) over the entire energy region

Oshima, C.; Aizawa, T.; Souda, Ryūtarō; Ishizawa, Y.; Sumiyoshi, Yoshihiro

doi:10.1016/0038-1098(88)90660-6

Cited by 193 publications

(127 citation statements)

References 15 publications

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“…For the TA mode at the M k-point, we find convergence toward 850 cm −1 , in good agreement with high-resolution electron energy loss spectroscopy on graphite, 39 but larger than 626 and 634 cm −1 calculated from LDA and GGA DFT calculations ͑Table V͒. The TA and TO modes are apparently not observed in the neutron scattering experiments.…”

Section: Phonon Dispersion Curvesupporting

confidence: 84%

Quantum mechanics based force field for carbon (QMFF-Cx) validated to reproduce the mechanical and thermodynamics properties of graphite

Pascal

Karasawa

Goddard

2010

The Journal of Chemical Physics

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As assemblies of graphene sheets, carbon nanotubes, and fullerenes become components of new nanotechnologies, it is important to be able to predict the structures and properties of these systems. A problem has been that the level of quantum mechanics practical for such systems ͑density functional theory at the PBE level͒ cannot describe the London dispersion forces responsible for interaction of the graphene planes ͑thus graphite falls apart into graphene sheets͒. To provide a basis for describing these London interactions, we derive the quantum mechanics based force field for carbon ͑QMFF-Cx͒ by fitting to results from density functional theory calculations at the M06-2X level, which demonstrates accuracies for a broad class of molecules at short and medium range intermolecular distances. We carried out calculations on the dehydrogenated coronene ͑C24͒ dimer, emphasizing two geometries: parallel-displaced X ͑close to the observed structure in graphite crystal͒ and PD-Y ͑the lowest energy transition state for sliding graphene sheets with respect to each other͒. A third, eclipsed geometry is calculated to be much higher in energy. The QMFF-Cx force field leads to accurate predictions of available experimental mechanical and thermodynamics data of graphite ͑lattice vibrations, elastic constants, Poisson ratios, lattice modes, phonon dispersion curves, specific heat, and thermal expansion͒. This validates the use of M06-2X as a practical method for development of new first principles based generations of QMFF force fields.

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Section: Phonon Dispersion Curvesupporting

confidence: 84%

Quantum mechanics based force field for carbon (QMFF-Cx) validated to reproduce the mechanical and thermodynamics properties of graphite

Pascal

Karasawa

Goddard

2010

The Journal of Chemical Physics

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“…Figure 1 shows the graphite phonon dispersion calculated with the optB88-vdW functional, starting from the optimized equilibrium structure, i.e., the optimized in-plane lattice constant a = 2.47Å and interlayer distance d = 3.36Å. The calculated phonon dispersions are in good agreement with experiments [63][64][65][66][67]. This is evident from Table II, which lists phonon frequencies at the high-symmetry points A, , M, and K, see also Ref.…”

Section: A Graphitesupporting

confidence: 66%

Li intercalation in graphite: A van der Waals density-functional study

2014

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Modeling layered intercalation compounds from first principles poses a problem, as many of their properties are determined by a subtle balance between van der Waals interactions and chemical or Madelung terms, and a good description of van der Waals interactions is often lacking. Using van der Waals density functionals we study the structures, phonons and energetics of the archetype layered intercalation compound Li-graphite. Intercalation of Li in graphite leads to stable systems with calculated intercalation energies of −0.2 to −0.3 eV/Li atom, (referred to bulk graphite and Li metal). The fully loaded stage 1 and stage 2 compounds LiC 6 and Li 1/2 C 6 are stable, corresponding to two-dimensional √ 3× √ 3 lattices of Li atoms intercalated between two graphene planes. Stage N > 2 structures are unstable compared to dilute stage 2 compounds with the same concentration. At elevated temperatures dilute stage 2 compounds easily become disordered, but the structure of Li 3/16 C 6 is relatively stable, corresponding to a √ 7× √ 7 in-plane packing of Li atoms. First-principles calculations, along with a Bethe-Peierls model of finite temperature effects, allow for a microscopic description of the observed voltage profiles.

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“…The phonon dispersion relationship predicted using this method, Fig. 6, demonstrates good agreement with the phonons measured using neutron and Raman scattering [26][27][28][29][30][31]. The AIMD phonon DOS at 300 K is compared to AILD in Fig.…”

Section: Graphite Phonon Dossupporting

confidence: 56%

Thermal neutron scattering law calculations using ab initio molecular dynamics

Wormald

Hawari

2017

EPJ Web Conf.

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Abstract. In recent years, methods for the calculation of the thermal scattering law (i.e. S(α, β), where α and β are dimensionless momentum and energy transfer variables, respectively) were developed based on ab initio lattice dynamics (AILD) and/or classical molecular dynamics (CMD). While these methods are now mature and efficient, further advancement in the application of such atomistic techniques is possible using ab initio molecular dynamics (AIMD) methods. In this case, temperature effects are inherently included in the calculation, e.g. phonon density of states (DOS), while using ab initio force fields that eliminate the need for parameterized semi-empirical force fields. In this work, AIMD simulations were performed to predict the phonon spectra as a function of temperature for beryllium and graphite, which are representative nuclear reactor moderator and reflector materials. Subsequently, the calculated phonon spectra were utilized to predict S(α, β) using the LEAPR module of the NJOY code. The AIMD models of beryllium and graphite were 5 × 5 × 5 crystal unit cells (250 atoms and 500 atoms respectively). Electronic structure calculations for the prediction of Hellman-Feynman forces were performed using density functional theory with a GGA exchange correlation functional and corresponding core electron pseudopotentials. AIMD simulations of 1000-10,000 time-steps were performed with the canonical ensemble (NVT thermostat) for several temperatures between 300 K and 900 K. The phonon DOS were calculated as the power spectrum of the AIMD predicted velocity autocorrelation functions. The resulting AIMD phonon DOS and corresponding inelastic thermal neutron scattering cross sections at 300 K, where anharmonic effects are expected to be small, were found to be in reasonable agreement with the results generated using traditional AILD. This illustrated the validity of the AIMD approach. However, since the impact of the temperature on the phonon DOS (e.g. broadening of spectral peaks) was observed in AIMD analysis, this technique may be envisioned as the approach for deriving the needed atomistic data for thermal scattering law calculations under realistic temperature and structural conditions for a given material.

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Surface phonon dispersion curves of graphite (0001) over the entire energy region

Cited by 193 publications

References 15 publications

Quantum mechanics based force field for carbon (QMFF-Cx) validated to reproduce the mechanical and thermodynamics properties of graphite

Quantum mechanics based force field for carbon (QMFF-Cx) validated to reproduce the mechanical and thermodynamics properties of graphite

Li intercalation in graphite: A van der Waals density-functional study

Thermal neutron scattering law calculations using ab initio molecular dynamics

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