Spatially heterogeneous dynamics investigated via a time-dependent four-point density correlation function

N. Lacevic, F. W. Starr, Thomas Schrøder, S. C. Glotzer

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    Resumé

    Relaxation in supercooled liquids above their glass transition and below the onset temperature of "slow" dynamics involves the correlated motion of neighboring particles. This correlated motion results in the appearance of spatially heterogeneous dynamics or "dynamical heterogeneity." Traditional two-point time-dependent density correlation functions, while providing information about the transient "caging" of particles on cooling, are unable to provide sufficiently detailed information about correlated motion and dynamical heterogeneity. Here, we study a four-point, time-dependent density correlation function g4(r,t) and corresponding "structure factor" S4(q,t) which measure the spatial correlations between the local liquid density at two points in space, each at two different times, and so are sensitive to dynamical heterogeneity. We study g4(r,t) and S4(q,t) via molecular dynamics simulations of a binary Lennard-Jones mixture approaching the mode coupling temperature from above. We find that the correlations between particles measured by g4(r,t) and S4(q,t) become increasingly pronounced on cooling. The corresponding dynamical correlation length xi4(t) extracted from the small-q behavior of S4(q,t) provides an estimate of the range of correlated particle motion. We find that xi4(t) has a maximum as a function of time t, and that the value of the maximum of xi4(t) increases steadily from less than one particle diameter to a value exceeding nine particle diameters in the temperature range approaching the mode coupling temperature from above. At the maximum, xi4(t) and the alpha relaxation time taualpha are related by a power law. We also examine the individual contributions to g4(r,t), S4(q,t), and xi4(t), as well as the corresponding order parameter Q(t) and generalized susceptibility chi4(t), arising from the self and distinct contributions to Q(t). These contributions elucidate key differences between domains of localized and delocalized particles
    OriginalsprogEngelsk
    TidsskriftJournal of Chemical Physics
    Vol/bind119
    Udgave nummer14
    Sider (fra-til)7372-7387
    ISSN0021-9606
    DOI
    StatusUdgivet - 2003

    Citer dette

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    title = "Spatially heterogeneous dynamics investigated via a time-dependent four-point density correlation function",
    abstract = "Relaxation in supercooled liquids above their glass transition and below the onset temperature of {"}slow{"} dynamics involves the correlated motion of neighboring particles. This correlated motion results in the appearance of spatially heterogeneous dynamics or {"}dynamical heterogeneity.{"} Traditional two-point time-dependent density correlation functions, while providing information about the transient {"}caging{"} of particles on cooling, are unable to provide sufficiently detailed information about correlated motion and dynamical heterogeneity. Here, we study a four-point, time-dependent density correlation function g4(r,t) and corresponding {"}structure factor{"} S4(q,t) which measure the spatial correlations between the local liquid density at two points in space, each at two different times, and so are sensitive to dynamical heterogeneity. We study g4(r,t) and S4(q,t) via molecular dynamics simulations of a binary Lennard-Jones mixture approaching the mode coupling temperature from above. We find that the correlations between particles measured by g4(r,t) and S4(q,t) become increasingly pronounced on cooling. The corresponding dynamical correlation length xi4(t) extracted from the small-q behavior of S4(q,t) provides an estimate of the range of correlated particle motion. We find that xi4(t) has a maximum as a function of time t, and that the value of the maximum of xi4(t) increases steadily from less than one particle diameter to a value exceeding nine particle diameters in the temperature range approaching the mode coupling temperature from above. At the maximum, xi4(t) and the alpha relaxation time taualpha are related by a power law. We also examine the individual contributions to g4(r,t), S4(q,t), and xi4(t), as well as the corresponding order parameter Q(t) and generalized susceptibility chi4(t), arising from the self and distinct contributions to Q(t). These contributions elucidate key differences between domains of localized and delocalized particles",
    author = "N. Lacevic and Starr, {F. W.} and Thomas Schr{\o}der and Glotzer, {S. C.}",
    year = "2003",
    doi = "10.1063/1.1605094",
    language = "English",
    volume = "119",
    pages = "7372--7387",
    journal = "Journal of Chemical Physics",
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    Spatially heterogeneous dynamics investigated via a time-dependent four-point density correlation function. / Lacevic, N.; Starr, F. W.; Schrøder, Thomas; Glotzer, S. C.

    I: Journal of Chemical Physics, Bind 119, Nr. 14, 2003, s. 7372-7387.

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    TY - JOUR

    T1 - Spatially heterogeneous dynamics investigated via a time-dependent four-point density correlation function

    AU - Lacevic, N.

    AU - Starr, F. W.

    AU - Schrøder, Thomas

    AU - Glotzer, S. C.

    PY - 2003

    Y1 - 2003

    N2 - Relaxation in supercooled liquids above their glass transition and below the onset temperature of "slow" dynamics involves the correlated motion of neighboring particles. This correlated motion results in the appearance of spatially heterogeneous dynamics or "dynamical heterogeneity." Traditional two-point time-dependent density correlation functions, while providing information about the transient "caging" of particles on cooling, are unable to provide sufficiently detailed information about correlated motion and dynamical heterogeneity. Here, we study a four-point, time-dependent density correlation function g4(r,t) and corresponding "structure factor" S4(q,t) which measure the spatial correlations between the local liquid density at two points in space, each at two different times, and so are sensitive to dynamical heterogeneity. We study g4(r,t) and S4(q,t) via molecular dynamics simulations of a binary Lennard-Jones mixture approaching the mode coupling temperature from above. We find that the correlations between particles measured by g4(r,t) and S4(q,t) become increasingly pronounced on cooling. The corresponding dynamical correlation length xi4(t) extracted from the small-q behavior of S4(q,t) provides an estimate of the range of correlated particle motion. We find that xi4(t) has a maximum as a function of time t, and that the value of the maximum of xi4(t) increases steadily from less than one particle diameter to a value exceeding nine particle diameters in the temperature range approaching the mode coupling temperature from above. At the maximum, xi4(t) and the alpha relaxation time taualpha are related by a power law. We also examine the individual contributions to g4(r,t), S4(q,t), and xi4(t), as well as the corresponding order parameter Q(t) and generalized susceptibility chi4(t), arising from the self and distinct contributions to Q(t). These contributions elucidate key differences between domains of localized and delocalized particles

    AB - Relaxation in supercooled liquids above their glass transition and below the onset temperature of "slow" dynamics involves the correlated motion of neighboring particles. This correlated motion results in the appearance of spatially heterogeneous dynamics or "dynamical heterogeneity." Traditional two-point time-dependent density correlation functions, while providing information about the transient "caging" of particles on cooling, are unable to provide sufficiently detailed information about correlated motion and dynamical heterogeneity. Here, we study a four-point, time-dependent density correlation function g4(r,t) and corresponding "structure factor" S4(q,t) which measure the spatial correlations between the local liquid density at two points in space, each at two different times, and so are sensitive to dynamical heterogeneity. We study g4(r,t) and S4(q,t) via molecular dynamics simulations of a binary Lennard-Jones mixture approaching the mode coupling temperature from above. We find that the correlations between particles measured by g4(r,t) and S4(q,t) become increasingly pronounced on cooling. The corresponding dynamical correlation length xi4(t) extracted from the small-q behavior of S4(q,t) provides an estimate of the range of correlated particle motion. We find that xi4(t) has a maximum as a function of time t, and that the value of the maximum of xi4(t) increases steadily from less than one particle diameter to a value exceeding nine particle diameters in the temperature range approaching the mode coupling temperature from above. At the maximum, xi4(t) and the alpha relaxation time taualpha are related by a power law. We also examine the individual contributions to g4(r,t), S4(q,t), and xi4(t), as well as the corresponding order parameter Q(t) and generalized susceptibility chi4(t), arising from the self and distinct contributions to Q(t). These contributions elucidate key differences between domains of localized and delocalized particles

    U2 - 10.1063/1.1605094

    DO - 10.1063/1.1605094

    M3 - Journal article

    VL - 119

    SP - 7372

    EP - 7387

    JO - Journal of Chemical Physics

    JF - Journal of Chemical Physics

    SN - 0021-9606

    IS - 14

    ER -