A rigorous approach to the formulation of extended Born‐Oppenheimer equation for a three‐state system |
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| Authors: | Biplab Sarkar Satrajit Adhikari |
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| Institution: | 1. Department of Chemistry, Indian Institute of Technology Guwahati, North Guwahati, Guwahati‐781 039, India;2. Department of Chemistry, North‐Eastern Hill University, Shillong‐793 022, India;3. Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata‐700 032, India |
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| Abstract: | If a coupled three‐state electronic manifold forms a sub‐Hilbert space, it is possible to express the non‐adiabatic coupling (NAC) elements in terms of adiabatic–diabatic transformation (ADT) angles. Consequently, we demonstrate: (a) Those explicit forms of the NAC terms satisfy the Curl conditions with non‐zero Divergences; (b) The formulation of extended Born‐Oppenheimer (EBO) equation for any three‐state BO system is possible only when there exists coordinate independent ratio of the gradients for each pair of ADT angles leading to zero Curls at and around the conical intersection(s). With these analytic advancements, we formulate a rigorous EBO equation and explore its validity as well as necessity with respect to the approximate one (Sarkar and Adhikari, J Chem Phys 2006, 124, 074101) by performing numerical calculations on two different models constructed with different chosen forms of the NAC elements. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 |
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| Keywords: | Born‐Oppenheimer treatment Non‐adiabatic coupling elements ADT Curl‐Divergence equation extended Born‐Oppenheimer equation |
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