Anisotropy of the chemical shift tensor for solid nitrogen

Ishol, L.M; Scott, Thomas Allan

doi:10.1016/0022-2364(77)90189-5

Cited by 21 publications

(10 citation statements)

References 10 publications

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“…Studies of solid nitrogen-argon mixtures [33][34][35] showed similar features to those referenced above for solid ortho-para H 2 mixtures. The randomness for the N 2 -Ar solid mixtures is introduced by the replacement of nitrogen molecules with argon atoms, which are spherically symmetrical and carry no electrostatic quadrupole moment.…”

Section: Orientational and Quadrupolar Glasses: Basicssupporting

confidence: 66%

Orientational Glasses: NMR and Electric Susceptibility Studies

et al. 2017

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Abstract:We review the results of a wide range of nuclear magnetic resonance (NMR) measurements of the local order parameters and the molecular dynamics of solid ortho-para hydrogen mixtures and solid nitrogen-argon mixtures that form novel molecular orientational glass states at low temperatures. From the NMR measurements, the distribution of the order parameters can be deduced and, in terms of simple models, used to analyze the thermodynamic measurements of the heat capacities of these systems. In addition, studies of the dielectric susceptibilities of the nitrogen-argon mixtures are reviewed in terms of replica symmetry breaking analogous to that observed for spin glass states. It is shown that this wide set of experimental results is consistent with orientation or quadrupolar glass ordering of the orientational degrees of freedom.

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Section: Orientational and Quadrupolar Glasses: Basicssupporting

confidence: 66%

Orientational Glasses: NMR and Electric Susceptibility Studies

et al. 2017

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Section: Nmr Study Of the Orientational Ordering Of Monolayers Of 15 mentioning

confidence: 99%

“…For T> 4 K the solid consists of a random mixture of 75% oand 25%/>-15 N 2 . The NMR spectrum of the ortho molecules is determined by the perturbation of the nuclear Zeeman Hamiltonian by the dipolar and anisotropic chemical shift Hamiltonians whose secular components are given by 14 ' 15 H £>i '=-(KD/3)P 2 (6 i )(3I 2 . 2 -2) , H Xi , -n Xac p 2 (e i )i g .. Q i specifies the orientation of the ith molecule with respect to the applied magnetic field (Z axis) (1) 658…”

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confidence: 99%

NMR Study of the Orientational Ordering of Monolayers ofN215on Graphite

Sullivan

Vaissière

1983

Phys. Rev. Lett.

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NMR pulse techniques have been used to study the orientational ordering of 15 N 2 molecules physisorbed on graphite. A small hysteresis (~2.5%) and small discontinuity in the evolution of the NMR echo amplitudes which depend directly on the local order parameters indicates that the order-disorder transition is first order.PACS numbers: 64.70. Kb, 76.60.Lz We report results of an NMR study of the orientational ordering of monolayers of 15 N 2 molecules physisorbed on exfoliated graphite. This system is a physical realization of the two-dimensional (2D) ordering of electric quadrupoles on a triangular lattice for which topological frustration and critical fluctuations are expected to play major roles. 1 ' 2 The transition from the orientationally disordered phase has stimulated considerable interest since it is believed to belong to the same universality class as the n = 3 component Heisenberg model with face-oriented anisotropy, and it is predicted that critical fluctuations will drive the transition first order. 1,3 ' 4 Although recent low-energy-electron diffraction measurements 5 * 6 have shown that the orientationally ordered phase is a (2x1) herringbone configuration, the nature of the phase transition has not been elucidated. In order to determine whether or not the transition is first order we have used NMR techniques to follow the evolution of the local order parameters. The results indicate that the transition is first order with a small discontinuity in the order parameter and a hysteresis ^ 2.5% on thermal cycling. This agrees qualitatively with recent Monte Carlo simulations. 3 Monolayers of N 2 form a commensurate 2D solid on graphite below 47 K with the molecules occupying the center of every third carbon ring, i.e., a {/ZxV~3)R3Q° triangular net. 7 At high temperatures, the molecular axes are disordered as a result of thermal agitation, but at low temperatures this rotational symmetry is broken by anisotropic forces acting on the molecules. There are two contributions: (1) the strong anisotropic potential of the graphite substrate 8 for which the molecules tend to lie parallel to the graphite, and (2) the anisotropic interaction between the molecules (principally electric quadrupole-quadrupole) which leads to a collective orientational ordering of the axes. 9 The results of en-ergy minimization, 10 Monte Carlo simulations, 11 and mean-field-approximation calculations 1 show that the ground state is a two-sublattice herringbone array.The orientational ordering transition was first seen in heat-capacity studies 12 and later confirmed by neutron scattering. 13 The herringbone structure was identified by low-energy electrondiffraction measurements 5 ' 6 which were able to detect several superlattice reflections. The intensity of the superlattice peaks varied continuously on warming with an apparently smooth transition at approximately 30 K although a weak intensity persisted up to 39 K. It was not possible to conclude from these studies whether the transition was smooth or first order.More detailed...

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“…Shielding anisotropies can be deduced either from solidstate NMR spectra [14][15][16] or determined in the gas phase by means of the molecular Zeeman effect. 1 However, large corrections for nuclear motions render a comparison of theory and experiment in both cases rather difficult.…”

Section: Introductionmentioning

confidence: 99%

Rovibrationally averaged nuclear magnetic shielding tensors calculated at the coupled-cluster level

Sundholm

Gauß

Schäfer

1996

The Journal of Chemical Physics

173

151

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A comparison of models for calculating nuclear magnetic resonance shielding tensors Multirank nuclear magnetic resonance studies of halfinteger quadrupolar nuclei in solids by threedimensional dynamicangle correlation spectroscopy Molecular quadrupole moment functions of HF and N2. I. Ab initio linearresponse coupledcluster results Nuclear magnetic shielding tensor functions for H 2 , HF, N 2 , CO, and F 2 are calculated at the coupled-cluster singles and doubles level augmented by a perturbative correction for triple excitations ͓CCSD͑T͔͒. The shielding constants for the lowest rovibrational states of these diatomics are obtained by solving the rovibrational Schrödinger equation with the finite-element method. For H, C, and F, absolute scales for the nuclear magnetic shielding constants have been obtained by combining computed diamagnetic shieldings with paramagnetic contributions deduced from measured spin-rotation constants and calculated rovibrational corrections. Since the experimental spin-rotation constants for N 2 and CO are inaccurate, shielding scales for N and O based on coupled cluster calculations are probably the most accurate available.

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Anisotropy of the chemical shift tensor for solid nitrogen

Cited by 21 publications

References 10 publications

Orientational Glasses: NMR and Electric Susceptibility Studies

Orientational Glasses: NMR and Electric Susceptibility Studies

NMR Study of the Orientational Ordering of Monolayers ofN215on Graphite

Rovibrationally averaged nuclear magnetic shielding tensors calculated at the coupled-cluster level

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