成键电子对- 小学生作文大全
化学成键的元素中的退化费米气体中的束缚电子对-《低温物理学报》... 化学成键的元素中的退化费米气体中的束缚电子对,陈羽;黄新民;-低温物理学报2012年第02期 ...
費米氣體
在物理学中，費米氣體，又稱為自由电子氣體、费米原子气体(fermionic atom gas)，是一个量子统计力学中的理想模型，指的是一群不相互作用的費米子。
費米氣體是理想氣體的量子力學版。在金屬內的電子、在半導體內的電子、或在中子星裏的中子，都可以被視為近似於費米氣體。在一個處於熱力平衡的費米氣體裏，費米子的能量分布，是由它們的密度，溫度，與容許能量量子態集合，依照費米-狄拉克統計的方程式而決定的。泡利不相容原理闡明，不容許被兩個或以上的費米子佔用同一个量子態。因此，在絕對零度，費米氣體的總能量，大於費米子數量與單獨粒子基態能量的乘積。並且，在絕對零度，費米氣體的壓力，稱為「簡併壓力」，不等於零。這與經典理想氣體的現象有很明顯的不同。簡併壓力使得中子星或白矮星能夠抵抗萬有引力的壓縮，因而得到穩定平衡，不致向內爆塌。
在低温下，玻色原子气体可以形成玻色-爱因斯坦凝聚(Bose-Einstein condensation, BEC)，这是由Einstein在1925年的理论而预言的。费米子由于泡利不相容原理，不能形成BEC。但可通过Feshbach共振，利用磁场调节费米原子间的相互作用，使费米子配对转变成玻色型粒子而形成BEC。
由於前述定義忽略了粒子與粒子之間的相互作用，費米氣體問題約化為研究一群獨立的費米子的物理行為的問題。這問題本身相當容易解析。一些更深奧，更進階，更精密的理論，牽涉到粒子與粒子之間的互相作用的理論（像費米液體理論或相互作用的微擾理論），時常會以費米氣體問題為研究的開端。
A Fermi gas is an ensemble of a large number of fermions. Fermions, named after Enrico Fermi, are particles that obey Fermi–Dirac statistics. These statistics determine the energy distribution of fermions in a Fermi gas in thermal equilibrium, and is characterized by their number density, temperature, and the set of available energy states.
By the Pauli exclusion principle, no quantum state can be occupied by more than one fermion with an identical set of quantum numbers. Thus a noninteracting Fermi gas, unlike a Bose gas, is prohibited from condensing into a Bose-Einstein condensate, although interacting Fermi gases might.[1] The total energy of the Fermi gas at absolute zero is larger than the sum of the single-particle ground states because the Pauli principle implies a sort of interaction or pressure that keeps fermions separated and moving. For this reason, the pressure of a Fermi gas is non-zero even at zero temperature, in contrast to that of a classical ideal gas. This so-called degeneracy pressure stabilizes a neutron star (a Fermi gas of neutrons) or a white dwarf star (a Fermi gas of electrons) against the inward pull of gravity, which would ostensibly collapse the star into a Black Hole. Only when a star is sufficiently massive to overcome the degeneracy pressure can it collapse into a singularity.
It is possible to define a Fermi temperature below which the gas can be considered degenerate (its pressure derives almost exclusively from the Pauli principle). This temperature depends on the mass of the fermions and the density of energy states. For metals, the electron gas's Fermi temperature is generally many thousands of kelvins, so in human applications they can be considered degenerate. The maximum energy of the fermions at zero temperature is called the Fermi energy. The Fermi energy surface in momentum space is known as the Fermi surface.
費米氣體
维基百科，自由的百科全书
費米氣體是理想氣體的量子力學版。在金屬內的電子、在半導體內的電子、或在中子星裏的中子，都可以被視為近似於費米氣體。在一個處於熱力平衡的費米氣體裏，費米子的能量分布，是由它們的密度，溫度，與容許能量量子態集合，依照費米-狄拉克統計的方程式而決定的。泡利不相容原理闡明，不容許被兩個或以上的費米子佔用同一个量子態。因此，在絕對零度，費米氣體的總能量，大於費米子數量與單獨粒子基態能量的乘積。並且，在絕對零度，費米氣體的壓力，稱為「簡併壓力」，不等於零。這與經典理想氣體的現象有很明顯的不同。簡併壓力使得中子星或白矮星能夠抵抗萬有引力的壓縮，因而得到穩定平衡，不致向內爆塌。
在低温下，玻色原子气体可以形成玻色-爱因斯坦凝聚(Bose-Einstein condensation, BEC)，这是由Einstein在1925年的理论而预言的。费米子由于泡利不相容原理，不能形成BEC。但可通过Feshbach共振，利用磁场调节费米原子间的相互作用，使费米子配对转变成玻色型粒子而形成BEC。
由於前述定義忽略了粒子與粒子之間的相互作用，費米氣體問題約化為研究一群獨立的費米子的物理行為的問題。這問題本身相當容易解析。一些更深奧，更進階，更精密的理論，牽涉到粒子與粒子之間的互相作用的理論（像費米液體理論或相互作用的微擾理論），時常會以費米氣體問題為研究的開端。
A Fermi gas is an ensemble of a large number of fermions. Fermions, named after Enrico Fermi, are particles that obey Fermi–Dirac statistics. These statistics determine the energy distribution of fermions in a Fermi gas in thermal equilibrium, and is characterized by their number density, temperature, and the set of available energy states.
By the Pauli exclusion principle, no quantum state can be occupied by more than one fermion with an identical set of quantum numbers. Thus a noninteracting Fermi gas, unlike a Bose gas, is prohibited from condensing into a Bose-Einstein condensate, although interacting Fermi gases might.[1] The total energy of the Fermi gas at absolute zero is larger than the sum of the single-particle ground states because the Pauli principle implies a sort of interaction or pressure that keeps fermions separated and moving. For this reason, the pressure of a Fermi gas is non-zero even at zero temperature, in contrast to that of a classical ideal gas. This so-called degeneracy pressure stabilizes a neutron star (a Fermi gas of neutrons) or a white dwarf star (a Fermi gas of electrons) against the inward pull of gravity, which would ostensibly collapse the star into a Black Hole. Only when a star is sufficiently massive to overcome the degeneracy pressure can it collapse into a singularity.
It is possible to define a Fermi temperature below which the gas can be considered degenerate (its pressure derives almost exclusively from the Pauli principle). This temperature depends on the mass of the fermions and the density of energy states. For metals, the electron gas's Fermi temperature is generally many thousands of kelvins, so in human applications they can be considered degenerate. The maximum energy of the fermions at zero temperature is called the Fermi energy. The Fermi energy surface in momentum space is known as the Fermi surface.
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