Neutron diffraction and electrical transport studies on the incommensurate magnetic phase transition in holmium at high pressures

Neutron diffraction and electrical transport measurements have been made on the heavy rare earth metal holmium at high pressures and low temperatures in order to elucidate its transition from a paramagnetic (PM) to a helical antiferromagnetic (AFM) ordered phase as a function of pressure. The electrical resistance measurements show a change in the resistance slope as the temperature is lowered through the antiferromagnetic Néel temperature. The temperature of this antiferromagnetic transition decreases from approximately 122 K at ambient pressure at a rate of -4.9 K GPa(-1) up to a pressure of 9 GPa, whereupon the PM-to-AFM transition vanishes for higher pressures. Neutron diffraction measurements as a function of pressure at 89 and 110 K confirm the incommensurate nature of the phase transition associated with the antiferromagnetic ordering of the magnetic moments in a helical arrangement and that the ordering occurs at similar pressures as determined from the resistance results for these temperatures.     

The inclusion of correlation in the calculation of phosphorus NMR chemical shieldings

The effects of including correlation in the calculation of phosphorus nuclear magnetic resonance (NMR) chemical shielding has been investigated for a variety of molecules in the Hartree-Fock, second-order Møller-Plesset (MP2), and estimated infinite-order Møller-Plesset theory ab initio approaches in the gauge including atomic orbital (GIAO) scheme. The inclusion of correlation in the shielding calculations often leads to significant changes from the Hartree-Fock theory and provides results that are in improved agreement with experiment. © 1996 John Wiley & Sons, Inc.     

33S NMR shieldings and chemical bonding in compounds of sulfur

Sulfur nuclear magnetic resonance (NMR) chemical shieldings have been determined at the correlation-including density functional theory scaled B3LYP/6-311+G(nd,p)//B3LYP/6-311+G(d,p) and modified MP2/6-311+G(nd,p) estimated infinite order Møller-Plesset levels with n = 2 for sulfur. The calculations span the range of sulfur shieldings and show agreement with experiment of about 3% of the shielding range. The atoms-in-molecules delocalization index and a covalent bond order from specific localized orbitals in the DFT approach are used to characterize sulfur's bonding and to relate it, where possible, to the calculated shieldings. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:216–224, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20000