Electron affinity defined

In some books, you will see electron affinity defined with an opposite-sign convention. Those values are actually the electron-gain enthalpies (Chapter 6). 

Table 5. Photoelectrical work function

Older chemical literature commonly uses the term electron affinity, defined as - A H%a. 

The LUMO energy is related to a molecular electron affinity, defined as the potential energy change involved in the process of moving an electron from rest at infinity into the LUMO of the molecule. Obviously, the LUMO position of the adsorbate determines the amount of excitation above the Fermi level that is required for resonant attachment. This explains why an important factor governing CT-PDIS is the position of the adsorbate affinity level. 

We also directly determined the ionisation potential from the HOMO-onset by a linear extrapolation and the secondary-electron cutoff and the electron affinity defined as the ionisation potential minus the optical band gap. 

Negative ions also have two unique thennodynainic quantities associated with them the electron affinity, EA, defined as the negative of the enthalpy change for addition of an electron to a molecule at 0 K [117. 121. 122]... 

TABLE 4.4 Electron Affinities of Atoms, Molecules, and Radicals Electron affinity of an atom (molecule or radical) is defined as the energy difference between the lowest (ground) state of the neutral and the lowest state of the corresponding negative ion in the gas phase. A(g) + e = A-(g) Data are limited to those negative ions which, by virtue of their positive electron affinity, are stable. Uncertainty in the final data figures is given in parentheses. Calculated values are enclosed in brackets. ... 

The electron affinity is defined as the energy released when an electron is added to a neutral molecule, computed as the energy difference between the neutral form and the anion. For example, the electron affinity of PH2 may be computed as ... 

The original paper defining the Gaussian-2 method by Curtiss, Raghavachari, Trucks and Pople tested the method s effectiveness by comparing its results to experimental thermochemical data for a set of 125 calculations 55 atomization energies, 38 ionization potentials, 25 electron affinities and 7 proton affinities. All compounds included only first and second-row heavy atoms. The specific calculations chosen were selected because of the availability of high accuracy experimental values for these thermochemical quantities. 

The energy change of reaction (12) is called the electron affinity of the fluorine atom. It is symbolized by E and, as defined here, is a negative quantity if heat is released when the ion is formed ... 

The propagator matrix is energy-dependent poles occur when E equals an ionization energy, Eo N)-En N-l),oi an electron affinity, Eo(N)-Em(N+1). Dyson orbitals (DOs) for ionization energies are defined by... 

Figure 16.1 The chemical hardness of an atom, molecule, or ion is defined to be half. The value of the energy gap between the bonding orbitals (HOMO—highest orbitals occupied by electrons), and the anti-bonding orbitals (LUMO—lowest orbitals unoccupied by electrons). The zero level is the vacumn level, so I is the ionization energy, and A is the electron affinity, (a) For hard molecules the gap is large (b) it is small for soft molecules. The solid circles represent valence electrons. Adapted from Atkins (1991).

The electron affinity of an element is defined as the amount of energy absorbed when an electron is added to an isolated gaseous atom to form an ion with a 1- charge. 

Electron affinity of an atom (molecule or radical) is defined as the energy difference between the lowest (ground) state of the neutral and the lowest state of the corresponding negative ion in the gas phase. 

The ionization potential and electron affinity of the molecule are I and A, respectively. By constmction, these definitions involve three Hamiltonians (IV-1, N, N+ 1). However, one may define Fukui functions without invoking any actual derivative relative to the number of electrons by using the derivative of the chemical potential relative to the potential [8]... 

We define here Wlh and W2h theories, respectively, as the modifications of Wl theory for which AVnZ basis sets are only used on elements of groups V, VI, VII, and VIII, but regular VnZ basis sets on groups I, II, III, and IV. (The h stands for heteroatom , as we originally investigated this for organic molecules.) For the purpose of the present paper, we have repeated the validation calculations described in the previous section for Wlh and W2h theories. (For about half of the systems, Wl and Wlh are trivially equivalent.) Some representative results can be found in Table 2.1 for atomization energies/heats of formation, and in Table 2.2 for ionization potentials and electron affinities. 

The electron affinity (EA) for a molecule is a quantity which is analogous to the ionization energy for cations. Thus, the electron affinity is defined as the negative of the enthalphy change for the electron attachment reaction ... 

The electron affinity EA is related to the energy of the lowest unoccupied molecular orbital and is defined as the enthalpy at 0 K for22 ... 

In the gas phase, homolytic bond dissociation enthalpies (D//) relate the thermochemical properties of molecules to those of radicals while ionization potentials (IP) and electron affinities (EA) tie the thermochemistry of neutral species to those of their corresponding ions. For example, Scheme 2.1 represents the relationships between RsSiH and its related radicals, ions, and radical ions. This representation does not define thermodynamic cycles (the H fragment is not explicitly considered) but it is rather a thermochemical mnemonic that affords a simple way of establishing the experimental data required to obtain a chosen thermochemical property. 

Spontaneous water-splitting upon illumination needs semiconductors with appropriate electron affinity and flat band conditions. The flat band positions shift with electrolyte pH. Hence, an external bias needs to be applied between the electrodes in most cases to effect water splitting. The external bias can be either electrical or chemical. This external bias contribution should be subtracted from (3.6.11) or (3.6.12) to get the overall photoconversion efficiency. In the case of an external electrical bias, the efficiency can be defined as ... 

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