The electrical resistivity and elastic constants of slowly cooled singlehyphen;crystal specimens of the ordered alloy Fe3Si (cubic, DO3structure) were measured from 4.2thinsp;deg;K to room temperature. The residual resistivity (rgr;o) was determined to be 0.6 mgr;OHgr;thinsp;cm. We infer from this that had the composition been exactly stoichiometric, which it was not, and the crystal free of internal voids generated during growth from the melt, the rgr;owould have approached zeromdash;a behavior that has not been reported previously for a (nonhyphen;superconducting) longhyphen;range ordered alloy. The temperature dependences of the directly measured adiabatic elastic constants were found to be as follows (uncorrected for thermal contraction;Tin deg;K):CL(T) =lcub;3.410minus;0.2696/lsqb;exp(367/T)minus;1rsqb;rcub;times;1011N/m2;C(T) =lcub;1.405minus;0.0563/lsqb;exp(227/T)minus;1rsqb;rcub; times;1011N/m2;Cprime; (T) =lcub;0.4183minus;0.1132/lsqb;exp(393/T)minus;1rsqb;rcub;times;1011N/m2. Calculated values for the isothermal Youngrsquo;s modulus (E), the shear modulus (G), and the Poisson ratio (ngr;) of a polycrystalline aggregate of Fe3Si possessing a random distribution of crystallite orientations are, forT=295thinsp;deg;K, as follows:E=2.15times;1011N/m2,G=0.828times;1011N/m2, and ngr;=0.299. The Debye temperature of the alloy at 0thinsp;deg;K is 501.1thinsp;deg;K.
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