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From: sra@oddjob.UUCP (Scott R. Anderson)
Newsgroups: net.physics
Subject: Real Physics -- Specific Heat of Glasses
Message-ID: <713@oddjob.UUCP>
Date: Sat, 11-May-85 02:42:52 EDT
Article-I.D.: oddjob.713
Posted: Sat May 11 02:42:52 1985
Date-Received: Sun, 12-May-85 04:56:54 EDT
References: <1397@mtx5b.UUCP> <>
Reply-To: sra@oddjob.UUCP (Scott R. Anderson)
Organization: University of Chicago, Department of Physics
Lines: 39
Summary: 

In article <1397@mtx5b.UUCP> mat@mtx5b.UUCP (Mark Terribile) writes:

>The specific heat of metals is very low ... approximately one fifth to
>one tenth that of water.  Ceramics and glassy materials have specific
>heats that are approximately the specific heat of water, give or take
>a factor of one part in three.
>	Is the specific heat of <a metallic glass> more reminiscent of the
>specific heat of the metallic phase of the material, or is it reminiscent
>of the specific heat of glass?

In article <> chas@gtss.UUCP (Charles Cleveland) writes:

>If you examine specific heats in some reasonable units (such as calories
>per degree kelvin per atom) you will find that there is no systematic
>variation is specific heats as one moves between materials belonging
>to the classes you consider...The variations do not particularly have
>to do with crystalline vs. amorphous or insulator vs. conductor.  These
>are about room temperature considerations (specific heat dominated by
>'lattice vibrations'.

    It should be pointed out that there is more than one kind of specific
heat:  Cv, the specific heat measured at constant volume, and Cp, the
specific heat measured at constant pressure.  What Charles refers to is
Cv, which is relatively constant amongst solids at room temperature.
However, it is much easier to measure Cp, so that is usually what is
reported in handbooks of materials.  I believe this is what Mark refers
to.  The difference between the two is an equation of thermodynamics
which involves the adiabatic and isothermal compressibilities of the
material.
    Cp for water is 1 cal/g-K (this is the definition of the calorie)
or 18 cal/mol-K, while most metals are about 5 cal/mol-K.  "Ordinary"
glasses are indeed around 20 cal/mol-K, but this is about half of the
specific heat of the corresponding liquid phase; the specific heat of
the glass phase is only slightly higher than that of the crystalline
phase.  The latter is also true of metallic glasses; i.e., the answer
to Mark's question is 'yes' (:-).

					Scott Anderson
					ihnp4!oddjob!kaos!sra