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adiabatic or diabatic Potential energy surfaces 相關(guān)翻譯！
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英語(yǔ)太蹩腳，加上專(zhuān)業(yè)詞匯多，困難太大，請(qǐng)各位高手幫忙！ Potential energy surfaces can be of two types: adiabatic or diabatic. Adiabatic surfaces are defined within the Born–Oppenheimer approximation by the energy (eigenvalue) of a given solution to the electronic Schrodinger equation at each geometry. Such solutions are obtained by using the full electronic Hamiltonian, that is, including kinetic energy, Coulomb, scalar relativistic and spin–orbit terms. Diabatic surfaces can be defined as generated from the eigenvalues of the Schrodinger equation solved using a Hamiltonian from which one or more terms have been omitted; in the present case, the spin–orbit coupling terms. Surfaces of both types are shown for a notional spin-forbidden reaction in Fig. 1. Reactants are on diabatic surface 1 (e.g. corresponding to a triplet state), with products on surface 2 (e.g. a singlet). The corresponding minima have different geometries, and the surfaces cross at the Minimum Energy Crossing Point (MECP). The adiabatic surfaces A and B in Fig. 1 do not cross, as the spin–orbit coupling matrix element H12 = <Ψ1|Hsoc|Ψ2> is non-zero and, therefore, when Hsoc is included in the Hamiltonian, the eigenfunctions are mixtures of different spin states. This means that, in principle, there is a well-defined transition state on the lower surface. In extreme cases, spin–orbit coupling may indeed be so strong that the mixing takes place over a broad range of geometries around the TS, and the reaction can in fact be described in the usual way using standard TST. In practice, for very many cases, the mixing is rather weak and non-adiabatic, non-Born–Oppenheimer behaviour will occur: the system will undergo ‘hops’ from one surface to the other. These can be described either in terms of the diabatic surfaces, as sudden changes in spin state, or in terms of the adiabatic surfaces, as sudden hops from the lower adiabatic surface, A, to the upper one, B. For example, in the limit of very weak spin-orbit coupling, a system approaching the crossing region from the reactant side is most likely, in diabatic terms, to remain on surface 1, and then return to reactants. In adiabatic terms, when the system approaches the very narrowly-avoided crossing between surfaces A and B it will ‘hop’ onto the upper surface. Upon returning from right to left on the diagram, it will hop again at the avoided crossing, back onto surface A and thereby head back to reactants. These two descriptions are equivalent, with the second perhaps more natural to theoretical chemists, but with the first more convenient for our purposes. We will therefore use the diabatic framework throughout. In this terminology, for reaction to occur, spin–orbit coupling must induce a ‘hop’ from surface 1 to surface 2 as the system goes through the crossing region. Hops can occur at any position along the reaction coordinate, but are more likely in the small region around the crossing point where the two surfaces are close in energy. |
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wanggang126(金幣+30, 翻譯EPI+1):翻譯的挺好，挺專(zhuān)業(yè)，大概能明白其中的意思了，太感謝你了！ 2010-05-07 23:28:39
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Potential energy surfaces can be of two types: adiabatic or diabatic. Adiabatic surfaces are defined within the Born–Oppenheimer approximation by the energy (eigenvalue) of a given solution to the electronic Schrodinger equation at each geometry. Such solutions are obtained by using the full electronic Hamiltonian, that is, including kinetic energy, Coulomb, scalar relativistic and spin–orbit terms. Diabatic surfaces can be defined as generated from the eigenvalues of the Schrodinger equation solved using a Hamiltonian from which one or more terms have been omitted; in the present case, the spin–orbit coupling terms. Surfaces of both types are shown for a notional spin-forbidden reaction in Fig. 1. Reactants are on diabatic surface 1 (e.g. corresponding to a triplet state), with products on surface 2 (e.g. a singlet). The corresponding minima have different geometries, and the surfaces cross at the Minimum Energy Crossing Point (MECP). 勢(shì)能面分為絕熱和非絕熱兩種。絕熱勢(shì)能面是在波恩-奧本海默近似的框架內(nèi)定義的，指的是在每個(gè)幾何構(gòu)型下，電子薛定諤方程的本征值，即能量。上述方程解對(duì)應(yīng)全電子哈密頓算符，即包括電子動(dòng)能，庫(kù)侖，標(biāo)量相對(duì)論和旋-軌各項(xiàng)。非絕熱勢(shì)能面可以由使用省略某（些）項(xiàng)的哈密頓的薛定諤方程的本征值解獲得；這里省略的是旋-軌項(xiàng)。圖一展示自旋禁阻反應(yīng)模型的兩種勢(shì)能面。反應(yīng)物在非絕熱勢(shì)能面1上（如，代表一個(gè)三重態(tài)），產(chǎn)物在勢(shì)能面2上（如，某個(gè)單重態(tài)）。相對(duì)應(yīng)的能量最小值處于不同的幾何構(gòu)型，勢(shì)能面相交于最小能量交叉點(diǎn)（MECP）處。 [ Last edited by c111999 on 2010-5-6 at 00:15 ] |
3樓2010-05-05 23:55:07
2樓2010-05-05 15:13:00
wanggang126(金幣+30):莫非你是研究這類(lèi)的？留個(gè)QQ以后多多向你請(qǐng)教！ 2010-05-07 23:30:16
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The adiabatic surfaces A and B in Fig. 1 do not cross, as the spin–orbit coupling matrix element H12 = <Ψ1|Hsoc|Ψ2> is non-zero and, therefore, when Hsoc is included in the Hamiltonian, the eigenfunctions are mixtures of different spin states. This means that, in principle, there is a well-defined transition state on the lower surface. In extreme cases, spin–orbit coupling may indeed be so strong that the mixing takes place over a broad range of geometries around the TS, and the reaction can in fact be described in the usual way using standard TST. In practice, for very many cases, the mixing is rather weak and non-adiabatic, non-Born–Oppenheimer behaviour will occur: the system will undergo ‘hops’ from one surface to the other. These can be described either in terms of the diabatic surfaces, as sudden changes in spin state, or in terms of the adiabatic surfaces, as sudden hops from the lower adiabatic surface, A, to the upper one, B. 圖一中的絕熱勢(shì)能面A和B不相交，因?yàn)樾?軌耦合矩陣元H12= <Ψ1|Hsoc|Ψ2>不為零，因此當(dāng)旋-軌項(xiàng)Hsoc包括在哈密頓中時(shí)，本征函數(shù)由不同自旋態(tài)混雜而成。這就意味著，理論上，低勢(shì)能面上有一個(gè)定義良好的過(guò)渡態(tài)。在極端的情況下，旋-軌耦合可能真的強(qiáng)到混雜可以在過(guò)渡態(tài)附近寬泛的幾何構(gòu)型間發(fā)生，反應(yīng)其實(shí)可以用標(biāo)準(zhǔn)的過(guò)渡態(tài)理論（TST）描述。實(shí)際上，在很多情況下，混雜很弱，將會(huì)發(fā)生非絕熱、非波恩-奧本海默行為：系統(tǒng)將從一個(gè)勢(shì)能面“躍遷”至另一個(gè)勢(shì)能面。這種情況可以用非絕熱勢(shì)能面描述，如自旋態(tài)突變，或用絕熱勢(shì)能面描述，如突然從低能量的絕熱勢(shì)能面A躍遷至高能絕熱勢(shì)能面B |
4樓2010-05-06 00:14:38
wanggang126(金幣+10):本來(lái)打算全部給你金幣的，但鑒于樓下的朋友也費(fèi)力不少，希望能理解！還是要感謝你的幫助！ 2010-05-07 23:34:00
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For example, in the limit of very weak spin-orbit coupling, a system approaching the crossing region from the reactant side is most likely, in diabatic terms, to remain on surface 1, and then return to reactants. In adiabatic terms, when the system approaches the very narrowly-avoided crossing between surfaces A and B it will ‘hop’ onto the upper surface. Upon returning from right to left on the diagram, it will hop again at the avoided crossing, back onto surface A and thereby head back to reactants. These two descriptions are equivalent, with the second perhaps more natural to theoretical chemists, but with the first more convenient for our purposes. We will therefore use the diabatic framework throughout. In this terminology, for reaction to occur, spin–orbit coupling must induce a ‘hop’ from surface 1 to surface 2 as the system goes through the crossing region. Hops can occur at any position along the reaction coordinate, but are more likely in the small region around the crossing point where the two surfaces are close in energy. 例如，在極弱旋-軌耦合極限，當(dāng)系統(tǒng)從反應(yīng)物一側(cè)接近交叉區(qū)域，用非絕熱術(shù)語(yǔ)表述為系統(tǒng)很有可能繼續(xù)待在勢(shì)能面1上，然后返回成反應(yīng)物。用絕熱術(shù)語(yǔ)表述為，當(dāng)系統(tǒng)進(jìn)入勢(shì)能面A與B間非常窄的擬交差區(qū)域，系統(tǒng)將躍遷至上層勢(shì)能面。一旦在圖中從右向左回到擬交差區(qū)域，系統(tǒng)會(huì)再次躍遷至勢(shì)能面A并且在此返回反應(yīng)物。這兩種描述是等價(jià)的，第二種對(duì)于理論化學(xué)工作者更自然，但是第一種更便于達(dá)到我們的目的。我們將通篇使用非絕熱框架。依此術(shù)語(yǔ)，為了讓反應(yīng)進(jìn)行，在系統(tǒng)通過(guò)交叉區(qū)域，旋-軌耦合必然引發(fā)從勢(shì)能面1至2的躍遷。躍遷可以在反應(yīng)坐標(biāo)上的任意某處發(fā)生，然而在兩個(gè)勢(shì)能面接近交叉點(diǎn)附近的小范圍內(nèi)更有可能。 [ Last edited by c111999 on 2010-5-6 at 00:37 ] |
5樓2010-05-06 00:31:07
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