arXiv subjects

Thiago Puccinelli

Publications and source records attributed to Thiago Puccinelli.

4 recordsLinked to original sources

arXiv2026

Activity and Competing Length Scales in an Anomalous Core-Softened Fluid

The interplay between activity and competing interaction length scales remains largely unexplored, despite its relevance to many soft and biological systems. Here, we study Active Brownian Particles interacting through a ramp-like core-softened potential that exhibits water-like anomalies in equilibrium. By varying the activity over a broad range of densities along two representative isotherms, one within the anomalous region and the other above it, we examine how self-propulsion modifies the structure and dynamics of the fluid. To gain microscopic insight into these changes, we construct effective interactions from the steady-state pair correlations using iterative Boltzmann inversion. We find that activity progressively suppresses the anomalies of the passive fluid, although signatures of the underlying structural crossover remain visible in normalized quantities. The effective interactions reveal that self-propulsion lowers the distinction between the local environments and facilitates population transfer between the two characteristic length scales. These results indicate that activity primarily acts by facilitating population transfer between the two local environments, thereby reducing the structural competition responsible for the anomalous response.

cond-mat.soft↗

arXiv2025

Stability and Dynamics of Sn-based Halide Perovskites: Insights from MACE-MP-0 and Molecular Dynamics Simulations

Tin-based halide perovskites have emerged as promising lead-free alternatives for optoelectronic applications, yet their structural stability and phase behavior at finite temperatures remain challenging to predict. Here, we assess the predictive capabilities of the foundational machine learning model MACE-MP-0 - trained on a broad chemical space and applied without system-specific fine-tuning - for the temperature-dependent behavior of CsSnBr3 and Cs2SnBr6. Molecular Dynamics simulations in the NpT ensemble were performed from 100 K to 500 K, and thermodynamic and structural descriptors including enthalpy, specific heat, radial distribution functions, translational order, bond angle distributions, and vibrational spectra were analyzed. Our results show that CsSnBr3 undergoes a low-temperature orthorhombic-to-cubic phase transition, evidenced by both the evolution of lattice parameters and subtle anomalies in enthalpy and specific heat, although the experimentally observed intermediate tetragonal phase is not captured. In contrast, Cs2SnBr6 remains cubic and maintains a more rigid octahedral framework across the entire temperature range. Overall, MACE-MP-0 qualitatively reproduces key thermal and structural features of these materials, highlighting its usefulness as a first step for studying new materials. For cases where capturing more subtle phase behavior is required, system-specific fine-tuning with Density Functional Theory data should be considered.

cond-mat.mtrl-sci↗

arXiv2025

Order-Disorder Transitions and Thermal Pathways in Frustrated 2D Colloidal Crystals

We employ extensive NPT molecular dynamics simulations to explore the thermal transitions of two-dimensional colloidal crystals interacting via a core-softened potential with competing length scales. The system stabilizes three distinct solid phases, namely low-density triangular (LDT), stripe, and kagome, which exhibit markedly different responses to heating and cooling. Our simulations reveal that the LDT and kagome phases melt via first-order transitions, but only the former recrystallizes smoothly. The kagome phase displays strong hysteresis and metastability, while the stripe phase undergoes a continuous and nearly reversible transformation. These results highlight the role of lattice geometry and frustration in shaping non-universal melting and freezing pathways in 2D soft matter.

cond-mat.soft↗

arXiv2025

Competing Length Scales and Symmetry Frustration Govern Non-Universal Melting in 2D Core-softened Colloidal Crystals

We investigate the melting behavior of two-dimensional colloidal crystals stabilized by a core-softened potential featuring two competing interaction length scales. Using molecular dynamics simulations, we analyze three polymorphic solid phases -- low-density triangular, stripe, and kagome -- and uncover distinct melting pathways. The triangular and kagome crystals undergo abrupt first-order transitions, driven by the interplay between energetic frustration and structural reorganization. In particular, the LDT phase melts through a sharp transition induced by a crossover between the two characteristic length scales. In contrast, the stripe phase exhibits a continuous transition with liquid-crystalline features: orientational and translational order decay gradually, while intra-stripe mobility persists, consistent with a KTHNY-like scenario. These findings demonstrate that melting in 2D soft-matter systems is inherently non-universal and governed by the competition between lattice symmetry, frustration, and multiple interaction scales. Our results provide microscopic insight into melting mechanisms beyond classical universality classes and offer guiding principles for the design of self-assembled materials with tunable phase behavior.

cond-mat.soft↗