Computational spectroscopy

Surface nitrosyl complexes of TMI have been thoroughly investigated by the computational spectroscopy [22,23,32,33,36,49], and their molecular structure has been ascertained by a remarkable agreement between the theory and experiment of both vibrational (oscillation frequencies and intensities) and magnetic (g and A tensors) parameters. The calculated pNO values for the examined mononitrosyls along with the experimental frequencies are listed in Table 2.6. Analogous collation of the IR data for dinitrosyl species is shown in Table 2.7. 

Pietrzyk, P., Zasada, F., Piskorz, W. et al. (2007) Computational spectroscopy and DFT investigations into nitrogen and oxygen bond breaking and bond making processes in model deNOx and deN20 reactions, Catal. Today, 119, 219. 

Regarding computation Spectroscopy and data processing are finally catching up with possibilities revealed by basic physical theory any detailed How-To given here would soon be obsolete. 

We hope that this review has shown that ever more elaborate experimental and computational techniques continue to be applied to elucidate the structure, assign spectra, and rationalize photochemical reaction mechanisms in transition metal carbonyl complexes. These systems provide a wealth of fascinating vibronically induced chemistry that we are only beginning to understand, and it is expected that as experimental and computational techniques further evolve many more studies of these systems will take place. Transition metal carbonyl systems are of primary importance in organometallic chemistry and unsaturated complexes are of key importance in industrial synthesis. Their photochemistry has many aspects that require a true multi-disciplinary approach, requiring knowledge and expertise in the fields of transition metal chemistry, ultrafast spectroscopy, computational spectroscopy, computational photochemistry and conical intersection theory, Jahn-Teller... 

Despite its importance, our knowledge about GO is still limited [27, 28], For example, due to its amorphous and nonstoichiometric character, the atomic structure of GO is not very clear. Many experimental studies on GO structure have been reported. However, structure characterization of systems as complicated as GO requires a combination of both experimental and theoretical efforts. Recently, there are significant progresses on the theoretical sides. First-principles calculations have been used to compare stabilities of different GO structure models. More importantly, computational spectroscopy strategy has also been used to make a direct comparison with experimental data and thus obtain deeper insights for GO structure. At the same time, electronic structure and other properties of GO can also be predicted by computational studies. The most difficult part is the understanding of the mechanisms of oxidation and reduction, which also requires an intense theoretical study. In this review, we will focus on recent progresses in theoretical studies on GO. Structure characterization based on computational spectroscopy is specially emphasized. 

There are mainly two reasons why so many GO structure models have been proposed in experiment. One reason is that GO samples vary from one batch to another under different synthesis conditions. Another reason is that assignment of spectroscopic data has been based on experiences on other molecules and materials and thus may not be very accurate. Theoretical studies are very useful in these two aspects. First-principles energetics can provide a clean simplified picture on GO structure, without the complexities of experimental conditions involved. On the other hand, computational spectroscopy provides a direct connection to experimental observations. 

As we have shown, based on first principles energetics, many GO stmcture models have been proposed. However, the power of energetics analysis is expected to be limited by the complexity of the GO potential energy surface, especially when artificial periodic boundary condition must be adopted with a small unit cell. In contrast, computational spectroscopy provides information, which can be directly compared with experiments. Therefore, it provides a powerful alternative in computational nanostructure characterization. XPS [37,48-52] and NMR [34-36, 53, 54] are two widely used experimental spectroscopic techniques to characterize local structures, and they are mostly used in GO structure research. 

Finally, based on computational spectroscopy we obtain a unified GO structure model, as shown in Fig. 5.4. Epoxy and hydroxyl groups prefer to aggregate, and they are in proximity with small area aromatic sp carbon. This represents the main feature of GO plane. When the degree of oxidation is high, there will also be a notable amount of epoxy pairs. At the edge of GO, there are -COOH, =0, and lactol groups. 

Zhang W, Carravetta V, Li Z, Luo Y, Yang J (2009) Oxidation states of graphene insights from computational spectroscopy. J Chem Phys 131 244505... 

Increased NIH funding has put a strain on national centers (computing, spectroscopy, etc.) for environmental projects... 

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