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Papers by Larry Finger

High-Temperature and High Pressure Crystal Chemistry, 2000

High-Temperature and High Pressure Crystal Chemistry, 2000

American Mineralogist, 1989

ACS Symposium Series, 1999

Microscopy and Microanalysis, 1997

Low-dose high resolution electron microscopy (HREM) is a useful technique for elucidating the str... more Low-dose high resolution electron microscopy (HREM) is a useful technique for elucidating the structure of zeolites. In recent years a number of zeolite structures have been solved using combinations of different characterization techniques including adsorption measurements, powder x-ray diffraction and low-dose high resolution electron microscopy (for example see ref. 2). We have used these techniques to study the structure of a novel zeolite material. However, great care must be exercised when interpreting data from these techniques in terms of crystal structural units. In this particular case, the structure was recently determined using single crystal x-ray diffraction and showed some surprises.Details of the synthesis of this zeolite are given elsewhere. The high adsorption capacity suggested that this zeolite possessed two interpenetrating channels (either a 10 and a 12 ring or two 12 ring channels). X-ray powder diffraction showed the material to be monoclinic with a= 18.5Å, b...

American Mineralogist, 1999

The crystal structure of (Mg 1.54 Li 0.23 Sc 0.23)Si 2 O 6 protopyroxene has been studied with si... more The crystal structure of (Mg 1.54 Li 0.23 Sc 0.23)Si 2 O 6 protopyroxene has been studied with single-crystal X-ray diffraction at pressures to 9.98 GPa and Raman spectroscopy to 10.4 GPa. A first-order displacive phase transformation from the Pbcn space group to P2 1 cn was observed between 2.03 and 2.50 GPa, which is characterized by a discontinuous decrease in a, c, and V by 1.1, 2.4, and 2.6%, respectively, and an increase in b by 0.9%, along with appearance of intensities of some 0kl reflections with k 2n. This is the first substantiated example of protopyroxene having the symmetry predicted by Thompson (1970). Evidence for the phase transition from Raman spectroscopy is also presented. The prominent structural changes associated with the Pbcn-to-P2 1 cn transformation involve the abrupt splitting of one type of O-rotated silicate chain in low-pressure protopyroxene into S-rotated A and O-rotated B chains in high-pressure protopyroxene, coupled with a marked decrease in the O3-O3-O3 angles and a re-configuration of O atoms around the M2 site. The kinking angle of the silicate chain in the low-pressure phase at 2.03 GPa is 165.9Њ, whereas the angles are 147.9Њ and 153.9Њ for the A and B chains, respectively, in highpressure phase at 2.50 GPa. Strikingly, the two types of silicate chains in the P2 1 cn structure alternate along the b axis in a tetrahedral layer parallel to (100). Such a mixed arrangement of two differently rotated silicate chains in a tetrahedral layer has not been observed in any other pyroxene structure. Compression anisotropy of the protopyroxene structure is affected by the phase transition. The relative linear compressibilities (␤ a :␤ b :␤ c) are 1.00:1.72:0.99 for low-pressure protopyroxene, but are 1.00:1.28:1.65 for high-pressure protopyroxene. The bulk moduli of low-and high-pressure phases are 130(3) and 111(1) GPa, respectively. This study concludes that the Pbcn-to-P2 1 cn phase transition results from the differential compression between SiO 4 tetrahedra and MO 6 octahedra.

American Mineralogist, 1996

Single-crystal X-ray diffraction data have been obtained at several pressures to 5.6 GPa for synt... more Single-crystal X-ray diffraction data have been obtained at several pressures to 5.6 GPa for synthetic LiScSi04 olivine. The bulk modulus is 118 :t I GPa, assuming K' = 4. This value is smaller than that of forsterite because compressibility of Li-O bonds in the M1 octahedral site is approximately twice that of the MP+-O bonds in other isomorphs.

Physical Review B, 1989

Solid neon was compressed under static conditions at 300 K to pressures in the 100 GPa (megabar) ... more Solid neon was compressed under static conditions at 300 K to pressures in the 100 GPa (megabar) range using diamond-anvil cell techniques. The crystal structure and P-V equation of state were determined by energy-dispersive x-ray diffraction with microcolhmated synchrotron radiation. Pressures were determined from ruby fluorescence spectra and from x-ray diffraction of tungsten powder contained within the sample. Solid neon remains an insulator with the fcc structure to the maximum pressure of 110 GPa at 300 K, where the compression V/Vo is 0.28. The 300-K P-Visotherm measured at high pressure is in excellent agreement with the results of electronic structure calculations but is incorrectly described by pure pair potentials recently developed for neon. These results indicate that there is a significant softening of the material by many-body interactions at high pressures. Finally, the measurements of ruby fiuorescence and tungsten x-ray diffraction in the neon medium obtained in this study provide an extension of the quasihydrostatic ruby pressure scale above 100 GPa.

Acta Crystallographica Section A Foundations of Crystallography, 2010

Physical Review Letters, 1990

Structural properties of CsI at high pressure have been investigated by the use of synchrotron x-... more Structural properties of CsI at high pressure have been investigated by the use of synchrotron x-raydiffraction techniques with the diamond-anvil cell at 300 K. The results indicate that the material undergoes a continuous distortion from 82 to an hcp-like phase, which is stable to at least 302 Gpa. The intermediate orthorhombic phase is geometrically different from previous assignments and-10% denser. %'ith the new structure, the p-V results of static pressure experiments, shock-wave studies, and theoretical calculations are now in good agreement.

Journal of Applied Crystallography, 1979

Deviations in the position of a crystal from the center of a goniostat and diffractometer alignme... more Deviations in the position of a crystal from the center of a goniostat and diffractometer alignment errors can be calculated from the observed angles for diffracted radiation. The present study includes a derivation of equations for the general setting (to :~ 0) and a scheme for transformation of these equations into other diffractometer coordinate systems. This method is illustrated by determination of centering errors for FeS in a diamond-anvil cell. In addition, unit-cell parameters for this crystal at high pressure are precisely determined with angular data collected by this technique.

High Pressure Research, 1992

Abstract We report results of high-pressure experiments with a new diamond-anvil cell in a monoch... more Abstract We report results of high-pressure experiments with a new diamond-anvil cell in a monochromatic, high-resolution x-ray scattering geometry with alinear position-sensitive detector. The experiments make possible the study of factors controlling line widths of diffraction profiles at pressures in the 100 GPa range, and demonstrate the potential for the use of line profile analysis and Rietveld refinement techniques with high-pressure powder diffraction data. Combined data for various materials indicate that relative contributions to linewidths due to particle size, intrinsic material strength, pressure and state of stress in the sample can be resolved. With light rare-gas solids as pressure-transmitting media, measured FWHMs of the order 0.03∘ 2 θ corresponding to resolution Δd/d of 2.5 × 10−3 for 2θ∼10-15∘ are reported. Formation of a high pressure phase appears to involve growth of submicron domains, judging from substantially broadened diffraction peaks under quasihydrostatic conditions. Detaile...

Geophysical Research Letters, 1990

The perovskite form of Mg0.981, Fe0.028Cr0.011 Si0.979 O3, quenched from 26 GPa and 2173 K in a u... more The perovskite form of Mg0.981, Fe0.028Cr0.011 Si0.979 O3, quenched from 26 GPa and 2173 K in a uniaxial split-sphere-type high-pressure apparatus, was studied at the SUNY X3A beamline at the National Synchrotron Light Source. With a Si (111) double-crystal monochromator and a single crystal of perovskite measuring 29×29×43 μm, intensities of 127 independent reflections were collected with sin θ/λ 3.5σI.

Europhysics Letters (EPL), 1994

ABSTRACT The pressure dependence of the structure of the pure fullerene C60 has been studied by h... more ABSTRACT The pressure dependence of the structure of the pure fullerene C60 has been studied by high-resolution synchrotron X-ray powder diffraction at 300 K in a diamond-anvil cell with fluid helium as a pressure-transmitting medium. Reflections corresponding to the simple cubic (s.c.) phase of C60 are identified at 2.5 GPa. The powder data agree well with calculated profiles for an ordered structure based on Pa symmetry and are consistent with a long-range orientational ordering transition under pressure identical to that occurring at 255 K and ambient pressure; the onset of the transition occurs below 0.5 GPa.

Chemical Communications, 1997

High-Temperature and High Pressure Crystal Chemistry, 2000

High-Temperature and High Pressure Crystal Chemistry, 2000

American Mineralogist, 1989

ACS Symposium Series, 1999

Microscopy and Microanalysis, 1997

Low-dose high resolution electron microscopy (HREM) is a useful technique for elucidating the str... more Low-dose high resolution electron microscopy (HREM) is a useful technique for elucidating the structure of zeolites. In recent years a number of zeolite structures have been solved using combinations of different characterization techniques including adsorption measurements, powder x-ray diffraction and low-dose high resolution electron microscopy (for example see ref. 2). We have used these techniques to study the structure of a novel zeolite material. However, great care must be exercised when interpreting data from these techniques in terms of crystal structural units. In this particular case, the structure was recently determined using single crystal x-ray diffraction and showed some surprises.Details of the synthesis of this zeolite are given elsewhere. The high adsorption capacity suggested that this zeolite possessed two interpenetrating channels (either a 10 and a 12 ring or two 12 ring channels). X-ray powder diffraction showed the material to be monoclinic with a= 18.5Å, b...

American Mineralogist, 1999

The crystal structure of (Mg 1.54 Li 0.23 Sc 0.23)Si 2 O 6 protopyroxene has been studied with si... more The crystal structure of (Mg 1.54 Li 0.23 Sc 0.23)Si 2 O 6 protopyroxene has been studied with single-crystal X-ray diffraction at pressures to 9.98 GPa and Raman spectroscopy to 10.4 GPa. A first-order displacive phase transformation from the Pbcn space group to P2 1 cn was observed between 2.03 and 2.50 GPa, which is characterized by a discontinuous decrease in a, c, and V by 1.1, 2.4, and 2.6%, respectively, and an increase in b by 0.9%, along with appearance of intensities of some 0kl reflections with k 2n. This is the first substantiated example of protopyroxene having the symmetry predicted by Thompson (1970). Evidence for the phase transition from Raman spectroscopy is also presented. The prominent structural changes associated with the Pbcn-to-P2 1 cn transformation involve the abrupt splitting of one type of O-rotated silicate chain in low-pressure protopyroxene into S-rotated A and O-rotated B chains in high-pressure protopyroxene, coupled with a marked decrease in the O3-O3-O3 angles and a re-configuration of O atoms around the M2 site. The kinking angle of the silicate chain in the low-pressure phase at 2.03 GPa is 165.9Њ, whereas the angles are 147.9Њ and 153.9Њ for the A and B chains, respectively, in highpressure phase at 2.50 GPa. Strikingly, the two types of silicate chains in the P2 1 cn structure alternate along the b axis in a tetrahedral layer parallel to (100). Such a mixed arrangement of two differently rotated silicate chains in a tetrahedral layer has not been observed in any other pyroxene structure. Compression anisotropy of the protopyroxene structure is affected by the phase transition. The relative linear compressibilities (␤ a :␤ b :␤ c) are 1.00:1.72:0.99 for low-pressure protopyroxene, but are 1.00:1.28:1.65 for high-pressure protopyroxene. The bulk moduli of low-and high-pressure phases are 130(3) and 111(1) GPa, respectively. This study concludes that the Pbcn-to-P2 1 cn phase transition results from the differential compression between SiO 4 tetrahedra and MO 6 octahedra.

American Mineralogist, 1996

Single-crystal X-ray diffraction data have been obtained at several pressures to 5.6 GPa for synt... more Single-crystal X-ray diffraction data have been obtained at several pressures to 5.6 GPa for synthetic LiScSi04 olivine. The bulk modulus is 118 :t I GPa, assuming K' = 4. This value is smaller than that of forsterite because compressibility of Li-O bonds in the M1 octahedral site is approximately twice that of the MP+-O bonds in other isomorphs.

Physical Review B, 1989

Solid neon was compressed under static conditions at 300 K to pressures in the 100 GPa (megabar) ... more Solid neon was compressed under static conditions at 300 K to pressures in the 100 GPa (megabar) range using diamond-anvil cell techniques. The crystal structure and P-V equation of state were determined by energy-dispersive x-ray diffraction with microcolhmated synchrotron radiation. Pressures were determined from ruby fluorescence spectra and from x-ray diffraction of tungsten powder contained within the sample. Solid neon remains an insulator with the fcc structure to the maximum pressure of 110 GPa at 300 K, where the compression V/Vo is 0.28. The 300-K P-Visotherm measured at high pressure is in excellent agreement with the results of electronic structure calculations but is incorrectly described by pure pair potentials recently developed for neon. These results indicate that there is a significant softening of the material by many-body interactions at high pressures. Finally, the measurements of ruby fiuorescence and tungsten x-ray diffraction in the neon medium obtained in this study provide an extension of the quasihydrostatic ruby pressure scale above 100 GPa.

Acta Crystallographica Section A Foundations of Crystallography, 2010

Physical Review Letters, 1990

Structural properties of CsI at high pressure have been investigated by the use of synchrotron x-... more Structural properties of CsI at high pressure have been investigated by the use of synchrotron x-raydiffraction techniques with the diamond-anvil cell at 300 K. The results indicate that the material undergoes a continuous distortion from 82 to an hcp-like phase, which is stable to at least 302 Gpa. The intermediate orthorhombic phase is geometrically different from previous assignments and-10% denser. %'ith the new structure, the p-V results of static pressure experiments, shock-wave studies, and theoretical calculations are now in good agreement.

Journal of Applied Crystallography, 1979

Deviations in the position of a crystal from the center of a goniostat and diffractometer alignme... more Deviations in the position of a crystal from the center of a goniostat and diffractometer alignment errors can be calculated from the observed angles for diffracted radiation. The present study includes a derivation of equations for the general setting (to :~ 0) and a scheme for transformation of these equations into other diffractometer coordinate systems. This method is illustrated by determination of centering errors for FeS in a diamond-anvil cell. In addition, unit-cell parameters for this crystal at high pressure are precisely determined with angular data collected by this technique.

High Pressure Research, 1992

Abstract We report results of high-pressure experiments with a new diamond-anvil cell in a monoch... more Abstract We report results of high-pressure experiments with a new diamond-anvil cell in a monochromatic, high-resolution x-ray scattering geometry with alinear position-sensitive detector. The experiments make possible the study of factors controlling line widths of diffraction profiles at pressures in the 100 GPa range, and demonstrate the potential for the use of line profile analysis and Rietveld refinement techniques with high-pressure powder diffraction data. Combined data for various materials indicate that relative contributions to linewidths due to particle size, intrinsic material strength, pressure and state of stress in the sample can be resolved. With light rare-gas solids as pressure-transmitting media, measured FWHMs of the order 0.03∘ 2 θ corresponding to resolution Δd/d of 2.5 × 10−3 for 2θ∼10-15∘ are reported. Formation of a high pressure phase appears to involve growth of submicron domains, judging from substantially broadened diffraction peaks under quasihydrostatic conditions. Detaile...

Geophysical Research Letters, 1990

The perovskite form of Mg0.981, Fe0.028Cr0.011 Si0.979 O3, quenched from 26 GPa and 2173 K in a u... more The perovskite form of Mg0.981, Fe0.028Cr0.011 Si0.979 O3, quenched from 26 GPa and 2173 K in a uniaxial split-sphere-type high-pressure apparatus, was studied at the SUNY X3A beamline at the National Synchrotron Light Source. With a Si (111) double-crystal monochromator and a single crystal of perovskite measuring 29×29×43 μm, intensities of 127 independent reflections were collected with sin θ/λ 3.5σI.

Europhysics Letters (EPL), 1994

ABSTRACT The pressure dependence of the structure of the pure fullerene C60 has been studied by h... more ABSTRACT The pressure dependence of the structure of the pure fullerene C60 has been studied by high-resolution synchrotron X-ray powder diffraction at 300 K in a diamond-anvil cell with fluid helium as a pressure-transmitting medium. Reflections corresponding to the simple cubic (s.c.) phase of C60 are identified at 2.5 GPa. The powder data agree well with calculated profiles for an ordered structure based on Pa symmetry and are consistent with a long-range orientational ordering transition under pressure identical to that occurring at 255 K and ambient pressure; the onset of the transition occurs below 0.5 GPa.

Chemical Communications, 1997