Angle calculations for a six-circle κ diffractometer

Thorkildsen, Gunnar; Mathiesen, Ragnvald H.; Larsen, Helge B.

doi:10.1107/s0021889899007347

Cited by 20 publications

(18 citation statements)

References 6 publications

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“…A signi®cant effort was invested in the optimization of the data-collection parameters. Station A of SNBL is equipped with a six-circle diffractometer from KUMA diffraction (KM6-CH) speci®-cally constructed for off-vertical plane diffractometry and this use of the diffractometer has been discussed previously (Thorkildsen et al, 1999(Thorkildsen et al, , 2000. Here, we used the diffractometer as a standard four-circle instrument with the detector circle (2) in the vertical plane to pro®t from the linear polarization of the radiation.…”

Section: Single-crystal Measurementsmentioning

confidence: 99%

The charge density of urea from synchrotron diffraction data

Birkedal

Madsen

Mathiesen³

et al. 2004

Acta Cryst Sect A

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111

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The charge density of urea is studied using very high precision single-crystal synchrotron-radiation diffraction data collected at the Swiss-Norwegian Beam Lines at ESRF. An unprecedented resolution of 1.44 A(-1) in sin theta;/lambda is obtained at 123 K. The optimization of the experiment for charge-density studies is discussed. The high precision of the data allowed the refinement of a multipole model extending to hexadecapoles and quadrupoles on the heavy and H atoms, respectively, as well as a liberal treatment of radial functions. The topological properties of the resulting electron density are analysed and compared with earlier experimental results as well as with periodic Hartree-Fock calculations. The properties of the strongly polarized C-O bond agree with trends derived from previous experimental results while the ab initio calculations differ significantly. The results indicate that the description of the C-O bond requires more flexible basis sets in the theoretical calculations. The calculated integrated atomic charges are much larger than the observed ones. It is suggested that the present experimental results provide new target values for validation of future ab initio calculations. The molecular dipole moment derived from the integrated atomic properties is the same as the one obtained from the multipole model even though the individual atomic contributions differ. Comparison with literature data for urea in solution and the gas phase yields a dipole enhancement in the solid of about 1.5 D. The thermal expansion of urea is determined using synchrotron powder diffraction data. With decreasing temperature, an increasing anisotropic strain is observed.

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Section: Single-crystal Measurementsmentioning

confidence: 99%

The charge density of urea from synchrotron diffraction data

Birkedal

Madsen

Mathiesen³

et al. 2004

Acta Cryst Sect A

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111

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“…The synchrotron storage ring was operating at 1.5 GeV and 200 mA. A newly constructed UHV-compatible six-circle soft X-ray diffractometer with geometry (Thorkildsen et al, 1999(Thorkildsen et al, , 2000 was used. A vacuum of 1.3 Â 10 À6 Pa was maintained to decrease the air absorption for X-rays with !…”

Section: Methodsmentioning

confidence: 99%

The phenomenon of polarization suppression of X-rayUmwegmultiple waves in crystals

Stetsko

Juretschke²,

Huang

et al. 2000

Acta Cryst Sect A

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The phenomenon of the polarization suppression of X-ray Umweg multiple waves in Renninger scans [Renninger (1937). Z. Kristallogr. 97, 107-121] of crystals, showing intensity decrease due to properly chosen wavelength and polarization of incident radiation, is observed. That is, one of the participating wave components in the multiple-wave interference is reduced considerably so that the intensity of multiple diffraction is decreased. The condition for total suppression of the multiple-wave interaction in crystals is derived theoretically from the Born approximation and verified with exact dynamical calculation and experiments. Partial suppression of the strong Umweg interfered component is demonstrated using elliptically or linearly polarized synchrotron radiation. The suppressed multiple-wave intensity distribution reveals high sensitivity to X-ray reflection phase. This multiple-diffraction technique under partial polarization suppression provides an alternative way of enhancing the visibility of multiple-wave interference in crystals for direct phase determination.

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“…The diffractometer, designed and fabricated in collaboration with Advanced Design Consulting USA, Inc. ͑Lansing, NY͒, consists of six rotation stages, four for sample alignment and two for detector alignment. While at least one other naming convention and set of angle calculations has been presented, 12 the basic naming convention used by You 11 has been adopted here but has been adapted to include a goniometer, which is comprised of the inner three sample rotation stages, K, , and K. The fourth sample rotation, , is used as the rotation in horizontal diffraction mode and is used to align the diffractometer in vertical diffraction mode by making the K axis perpendicular to the incident x-ray beam. This alignment must be done when the beam energy is changed because the beam direction changes when the side bounce monochromator is used to change the energy.…”

Section: A Diffractometermentioning

confidence: 99%

Six-circle diffractometer with atmosphere- and temperature-controlled sample stage and area and line detectors for use in the G2 experimental station at CHESS

Nowak

Blasini

Vodnick

et al. 2006

Review of Scientific Instruments

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A new diffractometer system was designed and built for the G2 experimental station at the Cornell High Energy Synchrotron Source (CHESS). A six-circle κ goniometer, which provides better access to reciprocal space compared to Eulerian cradles, was chosen primarily to perform large angle Bragg diffraction on samples with preferred crystallographic orientations, and can access both horizontal and vertical diffraction planes. A new atmosphere- and temperature-controlled sample stage was designed for thin film thermomechanical experiments. The stage can be operated in ultrahigh vacuum and uses a Be dome x-ray window to provide access to all scattering vectors above a sample’s horizon. A novel design minimizes sample displacements during thermal cycling to less than 160μm over 900°C and the stage is motorized for easy height adjustments, which can be used to compensate for displacements from thermal expansion. A new area detector was built and a new line detector was purchased. Both detectors cover a large region in reciprocal space, providing the ability to measure time-resolved phenomena. A detailed description of the design and technical characteristics is given. Some capabilities of the diffractometer system are illustrated by a strain analysis on a thin metal film and characterization of organic thin films with grazing incidence diffraction. The G2 experimental station, as part of CHESS, is a national user facility and is available to external users by application.

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Angle calculations for a six-circle κ diffractometer

Cited by 20 publications

References 6 publications

The charge density of urea from synchrotron diffraction data

The charge density of urea from synchrotron diffraction data

The phenomenon of polarization suppression of X-rayUmwegmultiple waves in crystals

Six-circle diffractometer with atmosphere- and temperature-controlled sample stage and area and line detectors for use in the G2 experimental station at CHESS

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