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  • 1
    Electronic Resource
    Electronic Resource
    Heat capacity and glass transition behavior of amorphous ice (1988)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 3323-3325 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100323a005
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  • 2
    Electronic Resource
    Electronic Resource
    Nature of the transformations of ice I and low-density amorphous ice to high-density amorphous ice (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7187-7192 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The changes of enthalpy at the irreversible transformation of high-density amorphous ice to low-density amorphous ice and of low-density amorphous ice to ice Ih have been measured in a Tian–Calvet heat-flow calorimeter. The equilibrium pressures of the two transformations have been estimated from the measured enthalpy and volume changes, neglecting the unknown, but small, entropy changes, as about 5 and 2 kbar, respectively. The course of the transformations has been followed in a piston-cylinder apparatus having an internal diameter of either 50 or 12 mm. The transformations are extraordinarily sharp when they are done slowly, the transformation pressure being constant to ±50 bar in 5 or 10 kbar in several transformations, although sometimes a sample transformed in two steps that were a few hundred bars apart. It seems that the activation volumes of the transformations are large and negative, and so the mechanism of the transformations is highly cooperative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457285
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  • 3
    Electronic Resource
    Electronic Resource
    Transformation of ice VIII to amorphous ice by "melting'' at low temperature (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2390-2392 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The melting curve of ice VIII near 25 kbar, which has a positive slope, has been estimated from various thermodynamic data and extrapolated approximately to 60 K at zero pressure. When ice VIII is heated from 77 K and ambient pressure it should, therefore, "melt,'' presumably below the glass transition. It has been shown to do so, and transforms to low-density amorphous ice when heated to about 125 K at ambient pressure. Ice I, whose melting curve has a negative slope, is already known to transform to a high-density amorphous ice at 77 K and 10 kbar, and so this and the present transformation are symmetrical equivalents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455981
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  • 4
    Electronic Resource
    Electronic Resource
    A 1H and 2H nuclear magnetic resonance study of amorphous ices at 77 K (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8503-8506 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The 2H quadrupole coupling constants (QCC) of deuteriated high-density amorphous (hda) ice and low-density amorphous (lda) ice were measured to be 226.6 and 218.6 kHz with asymmetry parameters (η) 0.106 and 0.104, respectively, at 77 K. Correlations of the QCC's with near-neighbor O–O distances in the crystalline phases of ice imply near-neighbor O–O distances of 2.84 and 2.79 A(ring) in high- and low-density amorphous ice, respectively, compared with values of 2.79 and 2.77 A(ring) for cubic ice (Ic) and hexagonal ice (Ih). The 1H second moment for hda ice of 37.5 G2 can be understood in terms of a short water interproton distance of 1.565 A(ring) and the greater density of hda ice with respect to ice Ih. The 1H spin-lattice relaxation times at 77 K for hda ice and lda ice at 124 and 773 s are much shorter than the value found for the crystalline ices. It is suggested that the T1 parameter may be useful in characterizing different amorphous ice phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462302
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure-induced phase transitions in clathrate hydrates (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 623-627 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ice I transforms to a high-density amorphous phase when pressed to 10 kbar at 77 K. Similar transformations in structure I and structure II clathrate hydrates have been studied by pressing samples in a piston-cylinder apparatus and by molecular dynamics simulations. The simulations were also carried out on structure I and II empty lattices. The hydrates and the empty lattices were found to transform to high-density phases under pressure at 77 K. The high-density phases of the empty lattices could be recovered at zero pressure, as is possible in the case of high-density amorphous phase of ice. However, it was not possible to recover the high-density phases of the hydrates at zero pressure. Instead, they reverted back to their original crystalline structures when the pressure was released. The molecular dynamics results suggest that under pressure the water molecules in the hydrates collapse around the guest molecules, and the repulsive forces between the guest and the water molecules are mainly responsible for the reversible transition to the original structure when the pressure is released.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460329
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  • 6
    Electronic Resource
    Electronic Resource
    The longitudinal-optic–tranverse-optic mode splitting in ice Ih (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7011-7012 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnitude of the longitudinal–transverse optic mode splitting on the 229 cm−1 infrared active band in the translational region of ice Ih is about 10 cm−1 as determined from an analysis of experimental infrared data. This agrees well with a recent calculation, and these results are used to give a precise assignment of the features in the vibrational density of states of ice Ih in the region 200–320 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461047
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  • 7
    Electronic Resource
    Electronic Resource
    X-ray diffraction and x-ray absorption studies of porous silicon, siloxene, heat-treated siloxene, and layered polysilane (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1946-1951 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several porous silicon, siloxene (Si6H6O3), heat-treated siloxene, and layered polysilane (Si6H6) samples have been studied with K- and L-edge x-ray photoabsorption, photoemission, and powder x-ray diffraction. The x-ray absorption of layered polysilane and porous-Si are found to be remarkably similar. In particular, the K absorption edges of these samples shift by about 0.4–0.6 eV to higher energy relative to crystalline silicon. Siloxene samples heated to 400 °C in inert gas are best described as a mixture of SiO2 and amorphous-Si. When heat-treated siloxene is studied by photoelectron spectroscopy (surface sensitive) it resembles SiO2, when it is studied by x-ray absorption (bulk and surface) features from both SiO2 and amorphous-Si are observed and when it is studied by x-ray diffraction (bulk measurement) it resembles amorphous-Si. The SiO2 is therefore predominantly at the surface and heat-treated siloxene is very small amorphous-Si particles coated with SiO2. The Si L edge of heat-treated siloxene is not shifted significantly with respect to crystalline Si, unlike that of porous-Si, as-prepared siloxene, or layered polysilane. Taken together, these results suggest that heat-treated siloxene does not resemble electrochemically prepared porous-Si but that it might resemble rapid thermal annealed porous-Si. On the other hand, we believe that layered polysilane and unheated porous-Si may be related.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356342
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of infrared absorptivities and line shapes and the distortion of anvils in diamond-anvil cells (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 767-771 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The infrared transmission of diamond and other transparent anvil apparatuses that contain absorbing samples, has been calculated as a function of frequency for planar anvils that are inclined to one another or that are distorted into parabolic shapes. At frequencies where the samples are completely transparent, the height of the interference fringes decreases with increase of frequency at nearly the same rate for both parabolically distorted and inclined anvils for which the maximum difference in optical path length of the sample is the same. Hence, the distortion of anvils in a typical experimental configuration have been measured up to a mean pressure on the anvil faces of 60 kbar. They are consistent with the predictions of elasticity theory that distortions occur at the rate of about 20 μm in 500 kbar. The predicted effect of such distortions on the absorbance, integrated area, and time autocorrelation function of the dipole moment is insignificant in a well-designed experiment, and so all these properties can now be measured accurately at high pressures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139825
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  • 9
    Electronic Resource
    Electronic Resource
    The nature of encapsulated silicon nanoclusters in zeolite Y (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 830-832 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Luminescent silicon clusters have been synthesized by chemical vapor deposition of Si2H6 into the supercages of H32Na24Y zeolite. The encapsulated Si clusters are air stable and exhibit a room-temperature photoluminescence in the green-yellow region. The electronic band gap of the cluster is determined to be about 2.4 eV from photoelectron and photoabsorption spectroscopies. A saturation loading of seven disilane molecules per supercage was determined directly from multiple quantum 1H nuclear magnetic resonance spin counting of the precursor material. Intrazeolitic Sin clusters are formed after heating with loss of SiH4 and H2. The new quantitative spin counting result is consistent with an average value of 12±2 Si/cluster obtained from previous indirect measurements using x-ray photoelectron spectroscopy and Si K-edge x-ray absorption near-edge spectroscopy [J. He, D. D. Klug, J. S. Tse, C. I. Ratcliffe, and K. F. Preston, Appl. Phys. Lett. 71, 3194 (1997)]. This observation reveals a mechanism for the conversion of gaseous Si2H6 into silicon nanoclusters. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123382
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular Perspectives on Structure and Dynamics in Clathrate Hydrates (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 715 (1994), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1994.tb38832.x
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