Electron affinity potential energy surfaces

Figure 20-3. Electron binding energies for molecule M in anionic state are defined pictorially in a representation of the potential energy surfaces of the neutral molecule (M) and anion radical (M ) with the lowest vibration energy level shown for each. During a vertical process, the geometry remains unchanged but for the adiabatic process structural relaxation occurs. Thus the VDE (vertical detachment energy) and VEA (vertical electron affinity) represent the upper and lower bounds to the adiabatic electron affinity (AEA)...

Figure 1. Potential energy surfaces as a function of bond angle for Lis, Lis and Lis " obtained from SCF-CI calculations at a bond distance of 5.6 a.u. a Cut in surfaces for Lis nd Lis. Key A, Lis, O, Lis Ai and %, Lis A2(Dsii). Various vertical electron affinities are represented, b Cut in surfaces for Lis nd Lis". Key O, Lis cind A, Lis". Various vertical ionization potentials are represented. Dissociation to Li + U2" at 5.24 eV (A).

The stationary point in octahedral symmetry is a genuine minimum on potential energy surface of SFg. This does not eliminate the possibility of the existence of local minima of lower symmetry with lower energy (which would increase the value of electron affinity). 

Besides geometric and vibrational properties, identification of the relative energies of compounds, or the energy differences between points on the potential energy surface of a particular compound have also been undertaken.[70-73] Calculations of the bond dissociation energy, reaction energy, electron affinity, heat of formation, and enthalpy of deprotonization are practical examples of the type of properties that have been determined for salts by using quantum chemistry methods. 

Potential energy surfaces (PES) of an anion formation (M ) after electron (e ) attachment to the neutral molecule (M). When the energy of an anion (M ) lies below the neutral molecule, positive electron affinity Is observed [left) otherwise the molecule is said to have negative electron affinity right). Energy changes shown for an electron attachment or detachment event are (1) the vertical electron affinity (VEA), (2) the adiabatic electron affinity (AEA), and (3) the vertical detachment energy (VDE). The VDE and VEA impose the upper and lower bounds to AEA... 

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