• Novel theory of entropy may solve materi

    From ScienceDaily@1:317/3 to All on Wednesday, March 16, 2022 22:30:42
    Novel theory of entropy may solve materials design issues

    Date:
    March 16, 2022
    Source:
    Penn State
    Summary:
    A challenge in materials design is that in both natural and
    humanmade materials, volume sometimes decreases, or increases, with
    increasing temperature. While there are mechanical explanations for
    this phenomenon for some specific materials, a general understanding
    of why this sometimes happens remains lacking.



    FULL STORY ==========================================================================
    A challenge in materials design is that in both natural and humanmade materials, volume sometimes decreases, or increases, with increasing temperature. While there are mechanical explanations for this phenomenon
    for some specific materials, a general understanding of why this sometimes happens remains lacking.


    ========================================================================== However, a team of Penn State researchers has come up with a theory to
    explain and then predict it: Zentropy.

    Zentropy is a play on entropy, a concept central to the second law of thermodynamics that expresses the measure of the disorder of a system
    that occurs over a period of time when there is no energy applied to
    keep order in the system. Think of a playroom in a preschool; if no
    energy is put into keeping it tidy, it quickly becomes disordered with
    toys all over the floor, a state of high entropy. If energy is put in
    via cleaning up and organizing the room once the children leave, then
    the room returns to a state of order and low entropy.

    Zentropy theory notes that the thermodynamic relationship of thermal
    expansion, when the volume increases due to higher temperature, is
    equal to the negative derivative of entropy with respect to pressure,
    i.e., the entropy of most material systems decreases with an increase
    in pressure. This enables Zentropy theory to be able to predict the
    change of volume as a function of temperature at a multiscale level,
    meaning the different scales within a system. Every state of matter has
    its own entropy, and different parts of a system have their own entropy.

    "When we talk about the configuration entropy (different ways particles rearrange within a system) that entropy is only part of the entropy of
    the system," said Zi-Kui Liu, Dorothy Pate Enright Professor of Materials Science and Engineering and primary investigator in the study. "So,
    you have to add the entropy of individual components of that system into
    the equation, and then you consider the different scales, the universe,
    the Earth, the people, the materials, these are different scales within different systems." The authors of the study, published in the Journal
    of Phase Equilibria and Diffusion, believe that Zentropy may be able
    to predict anomalies of other physical properties of phases beyond
    volume. This is because responses of a system to external stimuli are
    driven by entropy.



    ========================================================================== Macroscopic functionalities of materials stem from assemblies of
    microscopic states (microstates) at all scales at and below the scale
    of the macroscopic state of investigation. These functionalities are challenging to predict because only one or a few microstates can be
    considered in a typical computational approach such as the predictive
    "from the beginning" calculations, which help determine the fundamental properties of materials.

    "This challenge becomes acute in materials with multiple phase
    transitions, which are processes that convert matter from one state to
    another, such as vaporization of a liquid," Liu said. "This is often where
    the most transformative functionalities exist, such as superconductivity
    and giant electromechanical response." Zentropy theory "stacks" these different scales into an entropy theory that encompasses the different
    elements of an entire system, presenting a nested formula for the entropy
    of complex multiscale systems, according to Liu.

    "You have these different scales and you can stack them up with Zentropy theory," Liu said. "For example, atoms as a vibrational property, that's
    low scale, then you have electronic interaction, that even lower scale. So
    now how do you stack them together to cover the entire system? So that
    is what the Zentropy equation is about, stacking them together. It
    creates a partition function that is the sum of all the entropy scales."
    This approach has been something Liu's lab has worked on for more than
    10 years and five different published studies.



    ==========================================================================
    "The idea actually became very simple after we studied it and understood
    it," Liu said.

    Zentropy has potential to change the way materials are designed,
    especially those that are part of systems that are exposed to higher temperatures. These temperatures, given thermal expansion, could cause
    issues if the materials expand.

    "This has the potential to enable the fundamental understanding and design
    of materials with emergent properties, such as new superconductors and
    new ferroelectric materials that could potentially lead to new classes
    of electronics," Liu said. "Also, other applications such as designing
    better structural materials that withstand higher temperatures are also possible." While there are benefits for society in general, researchers
    could apply Zentropy to multiple fields. This is because of how entropy
    is present in all systems.

    "The Zentropy theory has the potential to be applied to larger systems
    because entropy drives changes in all systems whether they are black
    holes, planets, societies or forests," Liu said.

    Along with Liu, other authors of the study include Yi Wang, research
    professor in materials science and engineering, and Shun-Li Zhang,
    research professor in materials science and engineering. The work was
    supported by the National Science Foundation, the Department of Energy
    and the Department of Defense.


    ========================================================================== Story Source: Materials provided by Penn_State. Original written by
    Jamie C. Oberdick. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Zi-Kui Liu, Yi Wang, Shun-Li Shang. Zentropy Theory for Positive and
    Negative Thermal Expansion. Journal of Phase Equilibria and
    Diffusion, 2022; DOI: 10.1007/s11669-022-00942-z ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220316173307.htm

    --- up 2 weeks, 2 days, 10 hours, 50 minutes
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)