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A Sommerfeld expansion is an approximation method developed by Arnold Sommerfeld for a certain class of integrals which are common in condensed matter and statistical physics. Physically, the integrals represent statistical averages using the Fermi–Dirac distribution. When the inverse temperature is a large quantity, the integral can be expanded〔.〕〔http://www.physik.uni-regensburg.de/forschung/fabian/pages/mainframes/teaching/teaching_files/files%20of%20mf_statistical_physics/Sommerfeld.pdf〕 in terms of as : where is used to denote the derivative of evaluated at and where the notation refers to limiting behavior of order . The expansion is only valid if vanishes as and goes no faster than polynomially in as . == Application to the free electron model == Integrals of this type appear frequently when calculating electronic properties in the free electron model of solids. In these calculations the above integral expresses the expected value of the quantity . For these integrals we can then identify as the inverse temperature and as the chemical potential. Therefore, the Sommerfeld expansion is valid for large (low temperature) systems. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Sommerfeld expansion」の詳細全文を読む スポンサード リンク
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