Metastable anions

Particular care has been devoted to establishing a qualitatively correct description of the metastable anion state that arises. 

All in all, the bi-orthogonal dilated electron propagator offers a simple extension of the real electron propagator technique and with the incorporation of higher order decouplings like the E3, E ADC(3) etc. and suitably large and flexible basis sets should offer same power and effectiveness in the treatment of metastable anions and cations as done by its real counterpart for stable bound systems. 

If one attempts to study metastable anion states without carrying out such a stabilization study, one is doomed to failure, even if one employs an extremely large and flexible set of diffuse basis functions. In such a calculation, one will certainly obtain a large number of anion states with energies lying above that of the neutral, but one will not be able to select from these states the one that is the true resonance state because the true state will be buried in the myriad of states representing the N2 + e continuum. 

Readers who wish to learn more about how molecular EAs (and to a lesser extent, IPs) have been studied theoretically are directed to this author s web site http //simons.hec. utah.edu as well as to a series [38] of his reviews and chapters. The species that this group have examined include dipole-bound anions, zwitterion ions, conventional valence anions, multiply charged anions as well as a wide variety of metastable anions. 

Cooper CD, Comptrai RN (1972) Metastable anions of CO2. Chem Phys Lett 14 29-32... 

Finally, this chapter covers not just bound-state methods but also methods that can safely be applied to metastable anions (i.e., temporary anion resonances), which is a far less mainstream topic. For metastable anions, the emphasis of this chapter is on those methods that have been implemented in standard quantum chemistry codes and are therefore widely available to the chemistry community. 

This section defines and explains some basic chemical and quantum-mechanical concepts concerning anions. Bound anions (where M is lower in energy than M, at the minimum-energy geometry of the former) are considered first, and subsequently we discuss metastable anions, also known as temporary anion resonances. For easy reference, a list of acronyms is provided at the end of this chapter. 

While CCSD(T), MP2, DFT, and so on are appropriate for bound anions, theoretical description of metastable anions requires specialized techniques. Many of these techniques are well-established but have seen far less use as compared to bound-state quantum chemistry. In this chapter, we have discussed a variety of techniques (the maximum overlap method, CCR, and stabilization methods) that are all based, at some level, on modifications to bound-state quantum chemistry that can be implemented as reasonably straightforward modifications of standard bound-state quantum chemistry codes. It is this author s hope that this review of such methods for temporary anion resonances will prompt renewed and increased interest in these techniques. 

It is clear from Eqs. (31a) and (31b) that/(r) is the DPT analogue of the frontier orbital regioselectivity for nucleophiUc/ (r) and electrophilic/ (r) attack and it is a restatement of frrMitier molecular orbital (FMO) theory. However, the last statement may not be true because Fukui function includes the effect of electron correlation and orbital relaxation that are a priori neglected in FMO theory. Flurchik and Bartorotti [124] noticed considerable differences between HOMO/ LUMO density and Fukui function value. Chattaraj et al. [125] and Pacios et al. [126, 127] proposed gradient approximation for Fukui function to avoid the calculation of metastable anion to calculate Fukui function using finite difference approximation ... 

---