Golf-course and funnel energy landscapes: Protein folding concepts in martensites

TL;DR

This paper applies protein folding energy landscape concepts like golf-course and funnel to study phase transformations in martensites, revealing how entropy barriers influence transformation kinetics and structure formation.

Contribution

It extends protein folding energy landscape ideas to vector order parameters in martensites, analyzing transformation dynamics and entropy barriers.

Findings

Rapid conversions linked to large golf-course edges at low temperatures

Incubation delays associated with small golf-course edges and entropy barriers

Vogel-Fulcher divergence indicates dominant entropy barriers in transformation

Abstract

We use protein folding energy landscape concepts such as golf-course and funnel to study re-equilibration in athermal martensite parameter regime of triangle-to-centered rectangle, square-to-oblique, and triangle-to-oblique transitions under systematic temperature-quench Monte Carlo simulations. On quenching below a transition temperature, the seeded high-symmetry parent-phase austenite that converts to the low-symmetry product-phase martensite, through autocatalytic twinning or elastic photocopying, has both rapid conversions and incubation-delays in the temperature-time-transformation phase diagram. We find the rapid (incubation-delays) conversions at low (high) temperatures arises from the presence of large (small) size of golf-course edge that has funnel inside for negative energy states. In the incubating state, the strain structure factor enters into the Brillouin zone golf-course through searches for finite transitional pathways which closes off at the transition temperature with Vogel-Fulcher divergences that are insensitive to Hamiltonian energy scales and log-normal distributions, as signatures of dominant entropy barriers. The crossing of the entropy barrier is identified through energy occupancy distributions, Monte Carlo acceptance fractions, heat emission and internal work. The above ideas had previously been presented for the scalar order parameter case. Here we show similar results are also obtained for vector order parameters.