On the Location of Conical Intersections in CH2BrCl Using MS-CASPT2 Methods

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• 作者：Tam&aacute ; s Rozgonyi ; Leticia Gonz&aacute ; lez
• 刊名：Journal of Physical Chemistry A
• 出版年：2006
• 出版时间：August 31, 2006
• 年：2006
• 卷：110
• 期：34
• 页码：10251 - 10259
• 全文大小：469K
• 年卷期：v.110,no.34(August 31, 2006)
• ISSN：1520-5215

文摘

Multiconfigurational second-order perturbation theory has been employed to calculate two-dimensional potentialenergy surfaces for the lowest low-lying singlet electronic states of CH₂BrCl as a function of the two carbon-halogen bonds. The photochemistry of the system is controlled by a nonadiabatic crossing occurring betweenthe à and s/entities/Btilde.gif"> bands, attributed to the b¹A' and c¹A' states, which are found almost degenerate and forming anear-degeneracy line of almost equidistant C-Br and C-Cl bonds. A crossing point in the near-degeneracyline is identified as a conical intersection in this reduced two-dimensional space. The positions of the conicalintersection located at CASSCF, single-state (SS)-CASPT2, and multistate (MS)-CASPT2 levels of theoryare compared, also paying attention to the nonorthogonality problem of perturbative approaches. To validatethe presence of the conical intersection versus an avoided crossing, the geometrical phase effect has beenchecked using the multiconfigurational MS-CASPT2 wave function.