Temperature dependence of atomic relaxation and vibrations for the vicinal Ni(977) surface: a molecular dynamics study

Self Cite

Using molecular dynamics simulations and an analytic embedded-atom method, a comparative study of the surface anharmonicity for the close-packed surface of Mg (0001) and Al (111) is presented in the temperature range from 0 K to their melting temperatures. The temperature dependences of the surface phonon frequencies, the mean square vibrational amplitudes of surface atoms and the layer structure factor are calculated. The calculated results are in good agreement with the available experimental data. Although with the same atomic arrangement for the top layer, Al(111) preserves its crystalline order in the temperature range considered, and Mg(0001) exhibits surface melting. The possible mechanism for the different melting behaviors of the two surfaces is discussed.

Section: Introductionsupporting

confidence: 81%

Surface melting of close‐packed Mg(0001), compared with Al(111)

Yang¹,

Hu²,

Xiao³

et al. 2007

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“…The interactions between nickel atoms are described by a modified analytic embedded atom method (MAEAM) [14][15][16][17], which has been proven to be effective in the simulations of surfaces [14], nanostructures [15,16] and bulk materials [17]. In the present MAEAM, based on the early work of Johnson [18], we introduce a modified energy term M(P) to express the difference between the actual total energy of a system of atoms and that calculated from the original EAM using a linear superposition of spherical atomic electron densities.…”

mentioning

confidence: 99%

Vibrational properties in nanocrystalline nickels: temperature effects and composite model for thermodynamics

Tang¹,

Long

et al. 2008

Based on the atomic local structure, a nanocrystalline material is separated into two parts: inner grains and grain boundaries. Molecular dynamics simulations have been performed to study the difference in their vibrational properties in nanocrystalline nickels. The results obtained reveal that a similar phonon frequency softening as in the perfect lattice mainly focuses on grains in nanocrystalline materials, and for the grain boundary part there is no obvious change in the vibrational density of states in the temperature range 300–900 K, especially in the lower frequency range. Comparing with conventional crystals, the higher specific heat and vibrational entropy, and lower vibrational free energy with decreasing mean grain size, result from the high proportion of grain boundaries in nanocrystals. In addition, the composite model provides a good description of the contributions of grain and grain boundary phases to thermodynamic quantities. Supposing the nanocrystalline material can be treated as a composite composed of grain and grain boundary network, the vibrational thermodynamic quantities of the system can be well determined from the proportion of grain boundaries and the corresponding thermodynamic quantities of grain and grain boundary parts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

“…Our group proposed another modified method [14]. With introducing a modified energy term M(P) to the total energy expression to express the energy difference resulting from the electron density difference and to correct the negative Cauchy relation, a new type of modified analytic EAM (MAEAM) has been constructed for almost all typical metals [15][16][17][18][19][20]. We have developed and used our own MAEAM potential of fcc δ Pu to carry out MD simulation of small helium bubbles in Pu [21].…”

Section: The Potentialsmentioning

confidence: 99%

Interaction between helium and vacancy in plutonium by embedded atom method

Ao¹,

Wang²,

Hu³

et al. 2008

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The formation energies of small Hen Vm clusters (n and m denote the number of He atoms and vacancy, respectively) in Pu have been calculated with molecular dynamics (MD) simulations using the embedded atom method (EAM) potential, the Morse potential and the Lennard–Jones potential for describing the interactions of Pu–Pu, Pu–He and He–He, respectively. The binding energies of an interstitial He atom, an isolated vacancy and a self‐interstitial Pu atom to a Hen Vm cluster are also obtained from the calculated formation energies of the clusters. All the binding energies mainly depend on the He‐vacancy ratio (n /m) of clusters rather than the clusters size. With the increase of the n /m ratio, the binding energies of a He atom and a Pu atom to a Hen Vm cluster decrease with the ratio, and the binding energy of a vacancy to a Hen Vm cluster increases. He atoms act as a catalyst for the formation of Hen Vm clusters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)