Negative heat capacity at phase-separation in macroscopic systems

TL;DR

This paper discusses how systems with various interactions exhibit negative heat capacity during phase separation, a phenomenon observable in macroscopic systems under specific conditions, challenging traditional thermodynamic assumptions.

Contribution

It demonstrates that negative heat capacity at first-order phase transitions can occur in macroscopic systems when energy fluctuations are minimized, extending microcanonical ensemble insights.

Findings

Negative heat capacity occurs at phase separation.

Observable in macroscopic systems with suppressed energy fluctuations.

Challenges traditional thermodynamic assumptions.

Abstract

Systems with long-range as well with short-range interactions should necessarily have a convex entropy S(E) at proper phase transitions of first order, i.e. when a separation of phases occurs. Here the microcanonical heat capacity c(E)= -\frac{(\partial S/\partial E)^2}{\partial^2S/\partial E^2} is negative. This should be observable even in macroscopic systems when energy fluctuations with the surrounding world can be sufficiently suppressed.