Heat capacity, enthalpy fluctuations, and configurational entropy in broken ergodic systems

John Mauro, Roger J. Loucks, Sabyasachi Sen

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

A common assumption in the glass science community is that the entropy of a glass can be calculated by integration of measured heat capacity curves through the glass transition. Such integration assumes that glass is an equilibrium material and that the glass transition is a reversible process. However, as a nonequilibrium and nonergodic material, the equations from equilibrium thermodynamics are not directly applicable to the glassy state. Here we investigate the connection between heat capacity and configurational entropy in broken ergodic systems such as glass. We show that it is not possible, in general, to calculate the entropy of a glass from heat capacity curves alone, since additional information must be known related to the details of microscopic fluctuations. Our analysis demonstrates that a time-average formalism is essential to account correctly for the experimentally observed dependence of thermodynamic properties on observation time, e.g., in specific heat spectroscopy. This result serves as experimental and theoretical proof for the nonexistence of residual glass entropy at absolute zero temperature. Example measurements are shown for Corning code 7059 glass.

Original languageEnglish (US)
Article number164503
JournalJournal of Chemical Physics
Volume133
Issue number16
DOIs
StatePublished - Oct 28 2010

Fingerprint

Specific heat
Enthalpy
Entropy
enthalpy
specific heat
entropy
Glass
glass
Glass transition
absolute zero
curves
thermodynamic equilibrium
Thermodynamic properties
Spectroscopy
Thermodynamics
thermodynamic properties
formalism
spectroscopy

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

@article{aba422fa9988410ab5e4d9ba38caf869,
title = "Heat capacity, enthalpy fluctuations, and configurational entropy in broken ergodic systems",
abstract = "A common assumption in the glass science community is that the entropy of a glass can be calculated by integration of measured heat capacity curves through the glass transition. Such integration assumes that glass is an equilibrium material and that the glass transition is a reversible process. However, as a nonequilibrium and nonergodic material, the equations from equilibrium thermodynamics are not directly applicable to the glassy state. Here we investigate the connection between heat capacity and configurational entropy in broken ergodic systems such as glass. We show that it is not possible, in general, to calculate the entropy of a glass from heat capacity curves alone, since additional information must be known related to the details of microscopic fluctuations. Our analysis demonstrates that a time-average formalism is essential to account correctly for the experimentally observed dependence of thermodynamic properties on observation time, e.g., in specific heat spectroscopy. This result serves as experimental and theoretical proof for the nonexistence of residual glass entropy at absolute zero temperature. Example measurements are shown for Corning code 7059 glass.",
author = "John Mauro and Loucks, {Roger J.} and Sabyasachi Sen",
year = "2010",
month = "10",
day = "28",
doi = "10.1063/1.3499326",
language = "English (US)",
volume = "133",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "16",

}

Heat capacity, enthalpy fluctuations, and configurational entropy in broken ergodic systems. / Mauro, John; Loucks, Roger J.; Sen, Sabyasachi.

In: Journal of Chemical Physics, Vol. 133, No. 16, 164503, 28.10.2010.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Heat capacity, enthalpy fluctuations, and configurational entropy in broken ergodic systems

AU - Mauro, John

AU - Loucks, Roger J.

AU - Sen, Sabyasachi

PY - 2010/10/28

Y1 - 2010/10/28

N2 - A common assumption in the glass science community is that the entropy of a glass can be calculated by integration of measured heat capacity curves through the glass transition. Such integration assumes that glass is an equilibrium material and that the glass transition is a reversible process. However, as a nonequilibrium and nonergodic material, the equations from equilibrium thermodynamics are not directly applicable to the glassy state. Here we investigate the connection between heat capacity and configurational entropy in broken ergodic systems such as glass. We show that it is not possible, in general, to calculate the entropy of a glass from heat capacity curves alone, since additional information must be known related to the details of microscopic fluctuations. Our analysis demonstrates that a time-average formalism is essential to account correctly for the experimentally observed dependence of thermodynamic properties on observation time, e.g., in specific heat spectroscopy. This result serves as experimental and theoretical proof for the nonexistence of residual glass entropy at absolute zero temperature. Example measurements are shown for Corning code 7059 glass.

AB - A common assumption in the glass science community is that the entropy of a glass can be calculated by integration of measured heat capacity curves through the glass transition. Such integration assumes that glass is an equilibrium material and that the glass transition is a reversible process. However, as a nonequilibrium and nonergodic material, the equations from equilibrium thermodynamics are not directly applicable to the glassy state. Here we investigate the connection between heat capacity and configurational entropy in broken ergodic systems such as glass. We show that it is not possible, in general, to calculate the entropy of a glass from heat capacity curves alone, since additional information must be known related to the details of microscopic fluctuations. Our analysis demonstrates that a time-average formalism is essential to account correctly for the experimentally observed dependence of thermodynamic properties on observation time, e.g., in specific heat spectroscopy. This result serves as experimental and theoretical proof for the nonexistence of residual glass entropy at absolute zero temperature. Example measurements are shown for Corning code 7059 glass.

UR - http://www.scopus.com/inward/record.url?scp=78149380830&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78149380830&partnerID=8YFLogxK

U2 - 10.1063/1.3499326

DO - 10.1063/1.3499326

M3 - Article

C2 - 21033801

AN - SCOPUS:78149380830

VL - 133

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 16

M1 - 164503

ER -