arXiv subjects

Sándalo Roldán-Vargas

Publications and source records attributed to Sándalo Roldán-Vargas.

3 recordsLinked to original sources

arXiv2025

Competing structures in a minimal double-well potential model of condensed matter

The microscopic structure of several amorphous substances often reveals complex patterns such as medium- or long-range order, spatial heterogeneity, and even local polycrystallinity. To capture all these features, models usually incorporate a refined description of the particle interaction that includes an ad hoc design of the inside of the system constituents, and use temperature as a control parameter. We show that all these features can emerge from a minimal athermal two-dimensional model where particles interact isotropically by a double-well potential, which includes an excluded volume and a maximum coordination number. The rich variety of structural patterns shown by this simple geometrical model apply to a wide range of real systems including water, silicon, and different amorphous materials.

cond-mat.mtrl-sci↗

arXiv2024

Inspection paradox and jump detection in glassy systems

Dynamics in glassy systems near the phase transition is characterized by particle jumps. Approaches to describe these dynamics are based on models in which the time and length scales defining the jumps are parameters to be determined. We instead propose a model-independent method to detect these jumps. Our method uses the theory of the inspection paradox to analyze particle trajectories and reveals the time and length scales defining a jump without free parameters. Given its simplicity and generality, our method can be applied to resolve hopping motion in a broad class of systems, including experimental ones.

cond-mat.soft↗

arXiv2013

Phase Diagram of a Reentrant Gel of Patchy Particles

We study the phase diagram of a binary mixture of patchy particles which has been designed to form a reversible gel. For this we perform Monte Carlo and molecular dynamics simulations to investigate the thermodynamics of such a system and compare our numerical results with predictions based on the analytical parameter-free Wertheim theory. We explore a wide range of the temperature-density-composition space that defines the three-dimensional phase diagram of the system. As a result, we delimit the region of thermodynamic stability of the fluid. We find that for a large region of the phase diagram the Wertheim theory is able to give a quantitative description of the system. For higher densities our simulations show that the system is crystallizing into a BCC structure. Finally we study the relaxation dynamics of the system by means of the density and temperature dependences of the diffusion coefficient. We show that there exists a density range where the system passes reversibly from a gel to a fluid upon both heating and cooling, encountering neither demixing nor phase separation.

cond-mat.soft↗