arXiv subjects

Ashley Z. Guo

Publications and source records attributed to Ashley Z. Guo.

3 recordsLinked to original sources

arXiv2026

An Information-theoretic Collective Variable for Configurational Entropy

Entropy governs molecular self-assembly, phase transitions, and material stability, yet remains challenging to quantify and directly control in molecular systems. Here, we demonstrate that the computable information density (CID), a data compression-based information theoretic metric, provides a general per-configuration structural descriptor that tracks configurational entropy changes in molecular dynamics simulations, reflecting both local and long-range structural organization. We validate the CID across systems of increasing complexity, beginning with single-component Lennard-Jones melting before examining binary phase separation, polymer condensation and dispersion, and assembly of amorphous carbon networks at multiple densities. Unlike conventional order parameters, CID requires no a priori knowledge of relevant structural features and captures organizational signatures across a variety of molecular systems and discretization resolutions. By establishing a data compression-based structural complexity metric as a practical proxy for configurational entropy, this framework lays a foundation for future entropy-driven materials design and optimization strategies.

cond-mat.stat-mech↗

arXiv2025

Active diffusing crystals in a 2D non-equilibrium system

We investigate a 2D dynamical absorbing state model of monodisperse disks, in which rich phase behavior arises from interactions consisting solely of repulsive displacements between overlapping particles. The phase diagram reveals several unconventional features, including a disordered and static absorbing configuration, where no particles overlap, separated by a second-order phase transition to a continuously evolving active hexagonal crystal with collective ring diffusion, which in turn undergoes a first-order phase transition to an active isotropic liquid. The only driving parameter is $ε$, the maximum size of the random repulsive kicks. Small $ε$ facilitates self-organization into an ordered state, but large $ε$ prevents this organization from occurring. This is very different from typical order-disorder transitions, where there are two competing influences, energy and entropy, that drive the transition.

cond-mat.soft↗

arXiv2023

Dynamical approach to the jamming problem

A simple dynamical model, Biased Random Organization, BRO, appears to produce configurations known as Random Close Packing (RCP) as BRO's densest critical point in dimension $d=3$. We conjecture that BRO likewise produces RCP in any dimension; if so, then RCP does not exist in $d=1-2$ (where BRO dynamics lead to crystalline order). In $d=3-5$, BRO produces isostatic configurations and previously estimated RCP volume fractions 0.64, 0.46, and 0.30, respectively. For all investigated dimensions ($d=2-5$), we find that BRO belongs to the Manna universality class of dynamical phase transitions by measuring critical exponents associated with the steady-state activity and the long-range density fluctuations. Additionally, BRO's distribution of near-contacts (gaps) displays behavior consistent with the infinite-dimensional theoretical treatment of RCP when $d \ge 4$. The association of BRO's densest critical configurations with Random Close Packing implies that RCP's upper-critical dimension is consistent with the Manna class $d_{uc} = 4$.

cond-mat.stat-mech↗