Density functional theory computational analysis

A detailed structural analysis of a series of N-acetylated 4-DMAP salts using X-ray crystallography, variable-temperature IR and NMR spectroscopy as well as DFT (density functional theory) computation has been reported by Schreiner et al. 

Nalewajski, R. F. 2000. Coupling relations between molecular electronic and geometrical degrees of freedom in density functional theory and charge sensitivity analysis. Computers Chem. 24 243-257. 

A review of the Journal of Physical Chemistry A, volume 110, issues 6 and 7, reveals that computational chemistry plays a major or supporting role in the majority of papers. Computational tools include use of large Gaussian basis sets and density functional theory, molecular mechanics, and molecular dynamics. There were quantum chemistry studies of complex reaction schemes to create detailed reaction potential energy surfaces/maps, molecular mechanics and molecular dynamics studies of larger chemical systems, and conformational analysis studies. Spectroscopic methods included photoelectron spectroscopy, microwave spectroscopy circular dichroism, IR, UV-vis, EPR, ENDOR, and ENDOR induced EPR. The kinetics papers focused on elucidation of complex mechanisms and potential energy reaction coordinate surfaces. 

The measured electronic structure, occupied or unoccupied, provides the fullest information when also combined with theory. Electronic structure calculations in surface chemistry have advanced immensely in the past decades and have now reached a level of accuracy and predictive power so as to provide a very strong complement to experiment. Indeed, the type of theoretical modeling that will be employed and presented here can be likened to computer experiments, where it can be assumed that spectra can be computed reliably and thus computed spectra for different models of the surface adsorption used to determine which structural model is the most likely. In the present chapter, we will thus consistently use the interplay between experiment and theory in our analysis of the interaction between adsorbate and substrate. Before discussing what quantities are of interest to compute in the analysis of the surface chemical bond, we will briefly discuss and justify our choice of Density Functional Theory (DFT) as approach to spectrum and chemisorption calculations. 

During the past few decades, various theoretical models have been developed to explain the physical properties and to find key parameters for the prediction of the system behaviors. Recent technological trends focus toward integration of subsystem models in various scales, which entails examining the nanophysical properties, subsystem size, and scale-specified numerical analysis methods on system level performance. Multi-scale modeling components including quantum mechanical (i.e., density functional theory (DFT) and ab initio simulation), atom-istic/molecular (i.e., Monte Carlo (MC) and molecular dynamics (MD)), mesoscopic (i.e., dissipative particle dynamics (DPD) and lattice Boltzmann method (LBM)), and macroscopic (i.e., LBM, computational... 

R. Cammi, B. Mennucci, Structure and properties of molecular solutes in electronic excited states A polarizable continuum model approach based on the time-dependent density functional theory, in Radiation Induced Molecular Phenomena in Nucleic Acids A Comprehensive Theoretical and Experimental Analysis, ed. by M.K. Shukla, J. Leszczynski. Series Challenges and Advances in Computational Chemistry and Physics, vol 5 (Springer, Netherlands 2008)... 

The density functional theory and the cluster model approach enable the quantitative computational analysis of the adsorption of small chemical species on metal surfaces. Two studies are presented, one concerning the adsorption of acetylene on copper (100) surfaces, the other concerning the adsorption of ethylene on the (1(X)) surfaces of nickel, palladium and platinum. These studies support the usefulness of the cluster model approach in studies of heterogeneous catalysis involving transition metal catalysts. 

The applicability of the HK method for the pore size analysis of active carbons was questioned on the basis of adsorption isotherms obtained via density functional theory [19,20] as well as computer simulations [21,22]. The crudest assumption in this method is the use of the condensation approximation to represent the micropore filling, which in fact has a... 

We turn now to the analysis of pore structure. For this purpose, various optional computational procedures are incorporated in the software, which is now provided with most commercial adsorption equipment. For example, for micropore size analysis the isotherm can be converted into a t-plot and also displayed in either the Dubinin-Radushkevich (DR) or the Dubinin-Astakov (DA) coordinates. With some packages it is also possible to apply the MP method of Brunauer, the Horvath-Kawazoe (HK) method and/or density functional theory... 

Once the model is verified, e.g., through agreement between computed and experimental spectra, then it is possible to extract additional information on the bonding and interactions from the calculations that is not present in the experimental data [3], The experiment and typically Density Functional Theory (DFT) calculations go hand in hand and provide a full view of the electronic stracture and bond formation. Furthermore, XES provides a very strong basis for the evaluation of different theoretical methods for population analysis. Many different schemes subdividing the charge density into contributions assigned to specific atoms have been proposed, but the lack of means to directly measure the atomic populations in different orbitals has made aU methods somewhat arbitrary. The localized character of... 

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