Phase Transition in a Model of Y-Shaped Molecules

TL;DR

This paper investigates the phase behavior of Y-shaped molecules, like immunoglobulin, using Monte Carlo simulations on a hexagonal lattice, revealing their critical properties and phase transitions within the Ising universality class.

Contribution

The study provides the first detailed phase diagram of Y-shaped molecules and demonstrates their critical behavior using advanced simulation techniques and finite-size scaling analysis.

Findings

Identified the phase coexistence curve for Y-shaped molecules.

Determined the critical temperature, chemical potential, and density.

Confirmed the model belongs to the Ising universality class.

Abstract

In recent years the statistical mechanics of non-spherical molecules, such as polypeptide chains and protein molecules, has garnered considerable attention as their phase behavior has important scientific and health implications. One example is provided by immunoglobulin, which has a "Y"-shape. In this work, we determine the phase diagram of Y-shaped molecules on a hexagonal lattice through Monte Carlo Grand Canonical ensemble simulation, using histogram reweighting, multicanonical sampling, and finite-size scaling. We show that (as expected) this model is a member of the Ising universality class. For low temperatures, we implemented multicanonical sampling to induce faster phase transitions in the simulation. By studying several system sizes, we use finite-size scaling to determine the two phase coexistence curve, including the bulk critical temperature, critical chemical potential, and critical density.