Ground State Energy Difference of Hcp and Fcc Ortho-Hydrogens

Miyagi, Hiroshi; Nakamura, Tuto

doi:10.1143/ptp.37.641

Cited by 67 publications

(14 citation statements)

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“…Felsteiner 14 and also Miyagi and Nakamura 15 found that the rotational ground-state energy of pure ortho-H 2 was lower in the cubic phase than in the hep phase. The thermodynamic properties, with emphasis on the order-disorder transition temperatures T c in both crystalline phases, have been calculated.…”

Section: Theoretical and Experimental Surveymentioning

confidence: 93%

Study of Nuclear-Magnetic-Resonance Line Shapes in SolidH2

et al. 1969

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A detailed study of the NMR line shapes in solid H 2 has been carried out. The ortho-H 2 concentration c was between 0.09 and 0.95, and the temperature ranged from T=0.5 to 10°K. In the hep phase, a systematic compilation of the second and fourth moments as a function of c and T was made. In the cubic phase the splitting of the doublet structure was measured as a function of temperature. From an extrapolation of the measurements in the hep phase to the limiting case of pure ortho-H 2 , it is concluded that in the temperature region where thermal diffusion is unimportant, the second and fourth moments are independent of temperature, their values being, respectively, 80±2 kHz 2 and (14.8rfc0.8) X10 3 kHz 4 . The contribution to the second moment from intermolecular nuclear dipole interactions (this is the second moment extrapolated to T-oo) is obtained as a function of orthoconcentration and is compared with theoretical predictions. Good agreement is found if one takes into account the correlation between nearest H 2 neighbors, an effect that decreases the average value (R~3), where R is the distance between nearest neighbors. Experiments with 0.64

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Section: Theoretical and Experimental Surveymentioning

confidence: 93%

Study of Nuclear-Magnetic-Resonance Line Shapes in SolidH2

et al. 1969

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“…7 Inspection of the ground state energy E0 per molecule for singles, pairs, and three-particle 21 clusters and for pure o-H2 (Ref. 22) shows E0 to become more negative with increasing cluster size. Thus, it can be expected that the random distribution of the o-H2 impurities in the solid does not have the minimum free energy F. As T decreases, F is minimized if larger clusters are formed at the explense of isolated impurities.…”

Section: Orientational Energies and Quantum Diffusion A Short Reviewmentioning

confidence: 99%

NMR studies on single crystals of H2. III. Dynamic effects

1980

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The time-dependent effects in the NMR spectrum of ortho-Hz impurities in two single crystals of Hz are investigated over the temperature range between 0.02 and 3 K and for an ortho-Hz mole fraction X between 0.1% and 2%. The disappearance of the signal from isolated o-H2 impurities, after cooling the crystals to a given temperature, and the simultaneous increase of the signal from isolated o-H2 pairs indicates a clustering process. The characteristic times from both spectra are comparable and pass over a flat maximum near T = 0.3 K. The clustering process then accelerates drastically as T is decreased below 0.1 K. The characteristic times are only weakly dependent on the concentration X. Furthermore, the subsequent decay of the o-H2 pair signals with time suggests a slow diffusion of pairs and formation of larger clusters. It is found that the period associated with the decay of in-plane pairs (having their axis parallel to the basal plane) is considerably shorter than that for the out-of-plane pairs. The resui'ts are discussed in the light of the theory of hopping impurities (resonant ortho-para conversion) and possible coherent tunneling effects at low temperamres. Finally we briefly report some studies of the longitudinal relaxation time for the o-H2 pair NMR lines.

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“…1,2 This treatment was based on a knowledge of the molecular equilibrium orientations, as found from the ground state of a system of classical quadrupoles on a rigid fee lattice, 3 -4 and experiment. 5 " 8 Miyagi and Nakamura 9 have recently estimated the corrections to the ground-state energy for ortho-H 2 molecules on fee and hep lattices due to a spin-wave type zero-point energy. This effect was studied by considering rotational excitations in the ordered state, similar to spinwaves in antiferromagnets, where there is also a correction to the ground state as a result of the nonvanishing of a zero-point energy.…”

Section: Appendixmentioning

confidence: 99%

Elementary Excitations in fcc Solid Ortho-Hydrogen

1968

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An equation-of-motion formalism is used to give a nonlinear spin-wave treatment of fee solid orthohydrogen. The elementary excitations in ortho-hydrogen are librational waves and can be treated in a manner similar to spin waves in magnetism. The excitation spectrum, long-range order, and ground-state energy are calculated. It is found that the spin-wave excitations have a nonvanishing effect on both the long-range order and the ground-state energy. But, because of a large energy gap, the spin-wave-theory results deviate only slightly from their molecular-field values. ELEMENTARY EXCITATIONS IN fee. SOLID o-H 2

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Ground State Energy Difference of Hcp and Fcc Ortho-Hydrogens

Cited by 67 publications

References 0 publications

Study of Nuclear-Magnetic-Resonance Line Shapes in SolidH2

Study of Nuclear-Magnetic-Resonance Line Shapes in SolidH2

NMR studies on single crystals of H2. III. Dynamic effects

Elementary Excitations in fcc Solid Ortho-Hydrogen

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