Theoretical methods acronyms

The ASEP/MD method, acronym for Averaged Solvent Electrostatic Potential from Molecular Dynamics, is a theoretical method addressed at the study of solvent effects that is half-way between continuum and quantum mechanics/molecular mechanics (QM/MM) methods. As in continuum or Langevin dipole methods, the solvent perturbation is introduced into the molecular Hamiltonian through a continuous distribution function, i.e. the method uses the mean field approximation (MFA). However, this distribution function is obtained from simulations, i.e., as in QM/MM methods, ASEP/MD combines quantum mechanics (QM) in the description of the solute with molecular dynamics (MD) calculations in the description of the solvent. 

In physical and theoretical methods there has been a notable increase in the use of recently developed techniques - most of which have trendy acronyms. Thus DRAMA P NMR has been used to determine internuclear P-P distance in a phosphine sulfide 4,8-residue substituted decapeptide, and XANES has been applied to structural studies of phosphine selenides. In the mass spectral field MALDI-TOF has been found to be better than FAB for the determination of the mass spectra of nucleotide triphosphates, LA-FTICR has been used to study tris(cyanoethyl)phosphine and metaphosphates have been detected for the first time by laser photoionisation MS. ERMS was shown to be a powerful technique for the analysis of structurally similar organophosphate insecticides (OPs) and trace quantities of OPs can be determined by Cl using water as the ionising agent. 

The function of this chapter is to review these methods with emphasis on the types of phenomenology involved and information obtained. Many of the effects are complicated, and full theoretical descriptions are still lacking. The wide variety of methods and derivative techniques has resulted in a veritable alphabet soup of acronyms. A short list is given in Table VIII-1 (see pp. 313-318) the lUPAC recommendations for the abbreviations are found in Ref. 1. 

Despite the obvious limitation of the LCAO procedure as revealed by the Hj and H2 problems it still is the most popular scheme used in the theoretical study of polyatomic molecules. There is a bewildering number of approximate methods, commonly distinguished in terms of cryptic acronyms, designated as either ab initio or semi-empirical, but all of them based on the LCAO construction of molecular orbitals. The precise details can be found in many books and reviews. The present summary uses the discussion of Richards and Cooper [92] as a guide. 

Qualitative molecular-orbital theory approaches (and related qualitative treatments) are discussed throughout the text (particularly in Chapters 4 and 6), and a more detailed discussion of the contributions of such approaches presented in Chapter 8. As with the experimental methods discussed in Chapter 2, the topics presented in the present chapter are associated with numerous abbreviations and acronyms (and alternative titles). Both to serve as a key to these abbreviations, and as a source of reference to the numerous theoretical approaches now available, they are listed along with brief descriptions and references to further information in Appendix C. 

Numerous theoretical studies on DMABN have been carried out, and many of them confirm the greater validity of the TICT model. The main body of such calculations, however, has been limited to the isolated system, while few examples including solvent effects can be quoted. " On the contrary, the phenomenon is strongly related to solvation and thus explicit considerations of solvent interactions are very important to get a more accurate understamding of the experimental evidence on the specific effects due to the presence of polar solvents. Here we summarize the results of the correlated study of DMABN both in vacuo and in solution we have published on the Journal of American Chemical Society. In this study we have used the multireference perturbation configuration interaction (Cl) method, known with the CIPSI acronym, which has been coupled to the PCM-IEF solvation continuum model. ... 

The most widespread method, which can be applied to large systems, where the use of MC SCF or Coupled Clusters (an approximate singles-doubles CC2) methods is not possible, is density functional method (DFT). DFT is now an acronym for a variety of different approximations of the functional [90]. It has a comparatively low scaling with the system size and typically also has lower demands on the basis set. Its cost is similar to that of RHF model and nowadays it plays a dominant role in the theoretical investigations of the vibrational rotatory strength/ gi, go- The introduction of the DFT methods caused that the evaluation of rotatory strength became a routine procedure, now used to support experimental works. 

Some monographs helpful for readers have been published in the last few years. Helgaker, Jaszunski and Peeul summarized indirect spin-spin calculation methods, Autschbach and Zheng" discussed calculations of NMR parameters at the relativistic level, Vaara et al. discussed the anisotropic character of indirect spin-spin couplings, Tomasi, Meimuci and Cammi summarized solvation models useful in the calculations. In these works one can find theoretical backgrounds, experimental examples and explanation of acronyms. 

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