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The third law of thermodynamics is sometimes stated as follows, regarding the properties of systems in equilibrium at absolute zero temperature: At absolute zero (zero kelvin), the system must be in a state with the minimum possible energy, and the above statement of the third law holds true provided that the perfect crystal has only one minimum energy state. Entropy is related to the number of accessible microstates, and for a system consisting of many particles, quantum mechanics indicates that there is only one unique state (called the ground state) with minimum energy.〔J. Wilks ''The Third Law of Thermodynamics'' Oxford University Press (1961).〕 If the system does not have a well-defined order (if its order is glassy, for example), then in practice there will remain some finite entropy as the system is brought to very low temperatures as the system becomes locked into a configuration with non-minimal energy. The constant value is called the residual entropy of the system.〔Kittel and Kroemer, ''Thermal Physics'' (2nd ed.), page 49.〕 The Nernst–Simon statement of the third law of thermodynamics concerns thermodynamic processes at a fixed, low temperature: Here a condensed system refers to liquids and solids. A classical formulation by Nernst (actually a consequence of the Third Law) is: Physically, the Nernst–Simon statement implies that it is impossible for any procedure to bring a system to the absolute zero of temperature in a finite number of steps.〔Wilks, J. (1971). The Third Law of Thermodynamics, Chapter 6 in ''Thermodynamics'', volume 1, ed. W. Jost, of H. Eyring, D. Henderson, W. Jost, ''Physical Chemistry. An Advanced Treatise'', Academic Press, New York, page 477.〕 ==History== The 3rd law was developed by the chemist Walther Nernst during the years 1906–12, and is therefore often referred to as Nernst's theorem or Nernst's postulate. The third law of thermodynamics states that the entropy of a system at absolute zero is a well-defined constant. This is because a system at zero temperature exists in its ground state, so that its entropy is determined only by the degeneracy of the ground state. In 1912 Nernst stated the law thus: "It is impossible for any procedure to lead to the isotherm in a finite number of steps."〔Bailyn, M. (1994). ''A Survey of Thermodynamics'', American Institute of Physics, New York, ISBN 0–88318–797-3, page 342.〕 An alternative version of the third law of thermodynamics as stated by Gilbert N. Lewis and Merle Randall in 1923: :If the entropy of each element in some (perfect) crystalline state be taken as zero at the absolute zero of temperature, every substance has a finite positive entropy; but at the absolute zero of temperature the entropy may become zero, and does so become in the case of perfect crystalline substances. This version states not only Δ''S'' will reach zero at 0 K, but S itself will also reach zero as long as the crystal has a ground state with only one configuration. Some crystals form defects which causes a residual entropy. This residual entropy disappears when the kinetic barriers to transitioning to one ground state are overcome. With the development of statistical mechanics, the third law of thermodynamics (like the other laws) changed from a ''fundamental'' law (justified by experiments) to a ''derived'' law (derived from even more basic laws). The basic law from which it is primarily derived is the statistical-mechanics definition of entropy for a large system: : where ''S'' is entropy, ''kB'' is the Boltzmann constant, and is the number of microstates consistent with the macroscopic configuration. The counting of states is from the reference state of absolute zero, which corresponds to the entropy of S0. 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「Third law of thermodynamics」の詳細全文を読む スポンサード リンク
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