K. T. Faber Department of Materials Science and Engineering, Northwestern University Evanston, IL 60208 There is experimental evidence that stress-induced microcracking near a macrocrack tip enhances thefraclUre toughness of brittle materials. In considering the interaction of the macrocrack with multiple microcracks using a discrete model, it is essential to use approximation methods in order ...

The change in (1)H NMR chemical shifts upon hydrogen bonding was investigated using both experimental and theoretical methods. The (1)H NMR spectra of a number of phenols were recorded in CDCl(3) and DMSO solvents. For phenol, 2- and 4-cyanophenol and 2-nitrophenol the OH chemical shifts were measured as a function of concentration in CDCl(3). The plots were all linear with concentration, the g...

The results of a solid-state (11)B NMR study of a series of 10 boronic acids and boronic esters with aromatic substituents are reported. Boron-11 electric field gradient (EFG) and chemical shift (CS) tensors obtained from analyses of spectra acquired in magnetic fields of 9.4 and 21.1 T are demonstrated to be useful for gaining insight into the molecular and electronic structure about the boron...

Significant advances in NMR detection of insensitive, low-frequency spin-l/2 and quadrupolar nuclei have caused rapid progress in the application of transition metal NMR spectroscopy to organometallic chemistry. As a result, the structural dependence of metal NMR parameters, i.e. chemical shifts, heteronuclear and homonuclear spin coupling and relaxation times, has become a topical field of res...

Density-functional theory (DFT) calculations of the magnetic shielding for nuclear magnetic resonance (NMR) in solids provide an important contribution for understanding the experimentally observed chemical shifts. It is known that the calculated NMR shielding parameters for a particular nucleus in a series of compounds correlate well with the experimentally measured chemical shifts; however, t...

In 2001, Mauri and Pickard introduced the gauge including projected augmented wave (GIPAW) method that enabled for the first time the calculation of all-electron NMR parameters in solids, i.e. accounting for periodic boundary conditions. The GIPAW method roots in the plane wave pseudopotential formalism of the density functional theory (DFT), and avoids the use of the cluster approximation. Thi...

some of the adamantane properties were calculated in this study. chemical shift, free energy ofsolvation, free energy of cavity formation, henry's law constant, and other properties ofadamantane in dry phase, three solvents and three temperatures have been calculated with abinitio method base on density functional theory (dft) at b3lyp/6-31g, b31yp/6-31g*, b3lyp/6-31+g* and b3lyp/6-31++g** leve...

15N shielding tensors were determined for the central peptide groups in GGV, AGG, and APG by single-crystal NMR. We find that the angle between the downfield component (delta11) and the N-H or the N-C(delta) (pro) bonds is in the range of 20-23 degrees and in accord with previous solid-state NMR measurements. However, AGG, unlike APG or GGV, has a distorted peptide plane, and delta11 lies appro...