Structure and Inversion Barrier in AH Radicals

The structural data and inversion barriers of the AH radicals, collected in Tables 5 and 6, respectively, confirm the increasing degree of pyramidalization as A becomes a heavier group 14 atom the H-A-H bond angle p (= 120.00°, 112.66°, 112.44°, 110.56°) decreases and the inversion barrier corrected for 

Interhydrogen Steric Repulsion Versus A—H Electronic Interaction in AH3 Radicals 

To understand the trends in pyramidalization and inversion barrier of the four AH radicals, we divide the overall interaction energy AE between the central atom A and the three hydrogen atoms into three components as shown in Eq. [29], 

How are the various energy terms related to the electronic structure and the orbital interactions First, we consider the formation of the quartet (H )3 

We have analyzed the H H and A—H interactions for three geometries of each AH radical (Eq. [33]) (1) AH3-planar, the optimized planar structure (2) AH3-pyramidal, in which dAH is kept fixed to its value in the planar radical, whereas the H—A—H angle P is bent to its value in the optimized pyramidal structure (3) AH -pyramidal, the optimized pyramidal structure in which dAH is allowed to elongate to its equilibrium value. Note that for both CH3-pyramidal and CH3-pyramidal the optimum H-A-H angle p of 

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