NMR Chemical Shift Computation Ab Initio

Basis Sets Correlation Consistent Sets Benchmark Studies on Small Molecules Coupled-cluster Theory Gradient Theory M0ller-Plesset Perturbation Theory NMR Chemical Shift Computation Ab Initio Spin Contamination Symmetry in Chemistry. 

Nuclear magnetic resonance (NMR) is one of the major experimental tools in structural chemistry and biochemistry. The prediction of NMR shifts from ab initio calculations has been demonstrated for isolated molecules (see NMR Chemical Shift Computation Ab Initio), but the development of a practical ab initio approach for the calculation on NMR shifts in solids has been accomplished only quite recently. Based on DFT-LDA and a pseudopotential plane wave approach, these authors have presented an approach which promises to be useful in the investigation of NMR shifts in crystalline solids as well as in amorphous materials and liquids. As a demonstration of this approach, Mauri et al. have calculated the H NMR shifts of LiH and HF in the state of isolated molecules and in a crystal. In the case of LiH the results show very little change between the free molecule (a = 26.6 ppm) and the crystal (cr = 26.3 ppm). However, a significant change is found for the crystal at high pressures (65 GPa), where the chemical shift increases to 31.2 ppm. A quite different picture is obtained for the HF molecule, where the theory predicts a shift of 28.4 ppm in remarkable agreement with the experimental value of 28.4 ppm. For the HF crystal, a shift of... 

Another important second-order property, which is considerably improved by MP correlation effects is the NMR chemical shift (see NMR Chemical Shift Computation Ab Initio and NMR Chemical Shift Computation Structural Applications). Calculations by Gauss have shown that for C shifts accurate values are already obtained at the GIAO-MP2 level. Further improvements are obtained by GIAO-MP3 and GIAO-MP4(SDQ) calculations. In the case of molecules with multiple bonds such as N2, the inclusion of T effects... 

Basis Sets Correlation Consistent Sets Complete Active Space Self-consistent Field (CASSCF) Second-order Perturbation Theory (CASPT2) Configuration Interaction Coupled-cluster Theory Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field G2 Theory Geometry Optimization 1 Gradient Theory Inter-molecular Interactions by Perturbation Theory Molecular Magnetic Properties NMR Chemical Shift Computation Ab Initio NMR Chemical Shift Computation Structural Applications Self-consistent Reaction Field Methods Spin Contamination. 

Atoms in Molecules Electron Transfer Calculations Electronic Wavefunctions Analysis Hyperconjugation Intermolecular Interactions by Perturbation Theory Localized MO SCF Methods Natural Orbitals NMR Chemical Shift Computation Ab Initio Rotational Barriers Barrier Origins Valence Bond Curve Crossing Models. 

Density Functional Applications Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field NMR Chemical Shift Computation Ab Initio NMR Data Correlation with Chemical Structure NMR of Transition Metal Compounds. 

Infrared Data Correlations with Chemical Structure Infrared Spectra Interpretation by the Characteristic Frequency Approach Neural Networks in Chemistry NMR Chemical Shift Computation Ab Initio NMR Chemical Shift... 

Since about 1990, powerful post-Hartree-Fock approaches for the inclusion of electron correlation in chemical shift calculations have been developed and applied in main group chemistry (see NMR Chemical Shift Computation Ab Initio and NMR Chemical Shift Computation Structural Applications). Unfortunately, these correlated methods are computationally too demanding at present to be applied to transition metal complexes and clusters of chemically relevant size. In particular, the least expensive post-CHF method available, the MP2-GIAO approach, is expected to fail for systems with significant nondynamical correlation effects. 

Chemometrics Multivariate View on Chemical Problems Combinatorial Chemistry Factual Information Databases Fuzzy Methods in Chemistry Infrared Data Correlations with Chemical Structure Infrared Spectra Interpretation by the Characteristic Frequency Approach Inorganic Chemistry Databases Inorganic Compound Representation NMR Chemical Shift Computation Ab Initio NMR Chemical Shift Computation Structural Applications NMR Data Correlation with Chemical Structure Online Databases in Chemistry Spectroscopy Computational Methods Standard Exchange Formats for Spectral Data Structure and Substructure Searching Structure Determination by Computer-based Spectrum Interpretation Structure Generators Synthesis Design. 

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