skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Defect studies of molecular and rare-gas crystals down to 50 mK and up to 150 MPa

Abstract

Techniques have been developed to prepare single crystals of condensed gases of mm or larger size, to ascertain their degree of crystalline perfection and fix their orientation, to measure Bragg spacings, changes in Bragg spacings and intensities. For precise work at higher temperatures and pressures a Be specimen cell attached to a heat exchanger is used at the focus of a large orientable back-reflection camera. Phase transitions arising from changes in molecular rotational ordering in solid CH/sub 4/ and CD/sub 4/ and lattice parameters during sublimation and melting of solid Ar, Kr, and Xe have thus been studied. For lower temperatures, the x-ray scattering specimen cell is fixed to a helium dilution refrigerator; it can be taken down to 50 mK and internally pressurized to 20 MPa. The sealed-off x-ray source is orientable about three orthogonal axes. Scattered x-rays are collected in an orientable position-sensitive detector. Examples of investigations by coherent scattering include 1) determination of the symmetries of the different phases below 1 K of the system solid ortho- and para- H/sub 2/, and 2) microscopic study of isotopic phase separation in solid /sup 3/He-/sup 4/He mixtures below 0.4 K. In case 1), the known fcc form of solidmore » hydrogen, stable below about 2 K for ortho-rich material, was determined to transform to hcp form at lower concentrations and temperatures. The transformation temperatures and compositions could be followed, despite internal specimen heating due to spontaneous ortho- to paraconverision, below 200 mK. In case 2), x-ray studies of isotopic phase separation in /sup 3/He-/sup 4/He bcc solids were carried out by B. A. Fraass. Direct determination of Bragg spacings of the daughter phases and their perfection and orientation with respect to the matrix could be made for the first time, and new characteristics of the phase separation phenomena discovered as specimens were cooled and reheated in a range below 400 mK.« less

Authors:
Publication Date:
Research Org.:
Illinois Univ., Urbana (USA). Dept. of Physics
Sponsoring Org.:
USDOE
OSTI Identifier:
6128433
Report Number(s):
DOE/ER/01198-135; CONF-810386-1
ON: DE81026617; TRN: 81-015246
DOE Contract Number:  
AC02-76ER01198
Resource Type:
Conference
Resource Relation:
Conference: American Crystallographic Association meeting, College Station, TX, USA, Mar 1981
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DEUTERIUM COMPOUNDS; MOLECULAR CRYSTALS; HELIUM 3; HELIUM 4; HYDROCARBONS; HYDROGEN; METHANE; LATTICE PARAMETERS; X-RAY DIFFRACTION; XENON; ARGON; CRYSTAL DEFECTS; CRYSTAL-PHASE TRANSFORMATIONS; GRAIN ORIENTATION; KRYPTON; MONOCRYSTALS; RARE GASES; ULTRALOW TEMPERATURE; VERY HIGH PRESSURE; ALKANES; COHERENT SCATTERING; CRYSTAL STRUCTURE; CRYSTALS; DIFFRACTION; ELEMENTS; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; FLUIDS; GASES; HELIUM ISOTOPES; HYDROGEN COMPOUNDS; ISOTOPES; LIGHT NUCLEI; MICROSTRUCTURE; NONMETALS; NUCLEI; ORGANIC COMPOUNDS; ORIENTATION; PHASE TRANSFORMATIONS; SCATTERING; STABLE ISOTOPES; 360602* - Other Materials- Structure & Phase Studies; 656000 - Condensed Matter Physics

Citation Formats

Simmons, R O. Defect studies of molecular and rare-gas crystals down to 50 mK and up to 150 MPa. United States: N. p., 1981. Web.
Simmons, R O. Defect studies of molecular and rare-gas crystals down to 50 mK and up to 150 MPa. United States.
Simmons, R O. 1981. "Defect studies of molecular and rare-gas crystals down to 50 mK and up to 150 MPa". United States. https://www.osti.gov/servlets/purl/6128433.
@article{osti_6128433,
title = {Defect studies of molecular and rare-gas crystals down to 50 mK and up to 150 MPa},
author = {Simmons, R O},
abstractNote = {Techniques have been developed to prepare single crystals of condensed gases of mm or larger size, to ascertain their degree of crystalline perfection and fix their orientation, to measure Bragg spacings, changes in Bragg spacings and intensities. For precise work at higher temperatures and pressures a Be specimen cell attached to a heat exchanger is used at the focus of a large orientable back-reflection camera. Phase transitions arising from changes in molecular rotational ordering in solid CH/sub 4/ and CD/sub 4/ and lattice parameters during sublimation and melting of solid Ar, Kr, and Xe have thus been studied. For lower temperatures, the x-ray scattering specimen cell is fixed to a helium dilution refrigerator; it can be taken down to 50 mK and internally pressurized to 20 MPa. The sealed-off x-ray source is orientable about three orthogonal axes. Scattered x-rays are collected in an orientable position-sensitive detector. Examples of investigations by coherent scattering include 1) determination of the symmetries of the different phases below 1 K of the system solid ortho- and para- H/sub 2/, and 2) microscopic study of isotopic phase separation in solid /sup 3/He-/sup 4/He mixtures below 0.4 K. In case 1), the known fcc form of solid hydrogen, stable below about 2 K for ortho-rich material, was determined to transform to hcp form at lower concentrations and temperatures. The transformation temperatures and compositions could be followed, despite internal specimen heating due to spontaneous ortho- to paraconverision, below 200 mK. In case 2), x-ray studies of isotopic phase separation in /sup 3/He-/sup 4/He bcc solids were carried out by B. A. Fraass. Direct determination of Bragg spacings of the daughter phases and their perfection and orientation with respect to the matrix could be made for the first time, and new characteristics of the phase separation phenomena discovered as specimens were cooled and reheated in a range below 400 mK.},
doi = {},
url = {https://www.osti.gov/biblio/6128433}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1981},
month = {1}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share: