TY - JOUR

T1 - Relationship between neighbor number and vibrational spectra in disordered colloidal clusters with attractive interactions

AU - Yunker, Peter J.

AU - Zhang, Zexin

AU - Gratale, Matthew

AU - Chen, Ke

AU - Yodh, A. G.

PY - 2013/3/28

Y1 - 2013/3/28

N2 - We study connections between vibrational spectra and average nearest neighbor number in disordered clusters of colloidal particles with attractive interactions. Measurements of displacement covariances between particles in each cluster permit calculation of the stiffness matrix, which contains effective spring constants linking pairs of particles. From the cluster stiffness matrix, we derive vibrational properties of corresponding shadow glassy clusters, with the same geometric configuration and interactions as the source cluster but without damping. Here, we investigate the stiffness matrix to elucidate the origin of the correlations between the median frequency of cluster vibrational modes and average number of nearest neighbors in the cluster. We find that the mean confining stiffness of particles in a cluster, i.e., the ensemble-averaged sum of nearest neighbor spring constants, correlates strongly with average nearest neighbor number, and even more strongly with median frequency. Further, we find that the average oscillation frequency of an individual particle is set by the total stiffness of its nearest neighbor bonds; this average frequency increases as the square root of the nearest neighbor bond stiffness, in a manner similar to the simple harmonic oscillator.

AB - We study connections between vibrational spectra and average nearest neighbor number in disordered clusters of colloidal particles with attractive interactions. Measurements of displacement covariances between particles in each cluster permit calculation of the stiffness matrix, which contains effective spring constants linking pairs of particles. From the cluster stiffness matrix, we derive vibrational properties of corresponding shadow glassy clusters, with the same geometric configuration and interactions as the source cluster but without damping. Here, we investigate the stiffness matrix to elucidate the origin of the correlations between the median frequency of cluster vibrational modes and average number of nearest neighbors in the cluster. We find that the mean confining stiffness of particles in a cluster, i.e., the ensemble-averaged sum of nearest neighbor spring constants, correlates strongly with average nearest neighbor number, and even more strongly with median frequency. Further, we find that the average oscillation frequency of an individual particle is set by the total stiffness of its nearest neighbor bonds; this average frequency increases as the square root of the nearest neighbor bond stiffness, in a manner similar to the simple harmonic oscillator.

UR - http://www.scopus.com/inward/record.url?scp=84875794866&partnerID=8YFLogxK

U2 - 10.1063/1.4774076

DO - 10.1063/1.4774076

M3 - Article

AN - SCOPUS:84875794866

SN - 0021-9606

VL - 138

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

IS - 12

M1 - 12A525

ER -