We study the microscopic origins of relaxation modes revealed by spectroscopic studies of glasses. Major features in calorimetric and structural relaxation spectra, including $\alpha$ peaks, $\beta$ peaks, and excess wings, are reproduced using a distinguishable-particle lattice model. It is based on void-induced particle hops, which model stringlike particle hopping motions. Excess wings are found to be flattened variants of $\beta$ peaks when particle hopping barriers admit a wide distribution. A $\beta$ relaxation event is attributed to the hop of a particle which neighbors a void. An $\alpha$ relaxation event involves a similar process by an arbitrary particle but also includes, as a prior step, the arrival of a diffusing void to become its neighbor.

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• Glass transition
• Glassy systems
• Monte Carlo methods