\ensuremath{\alpha}-quartz-type ${\mathrm{GeO}}_{2}$ was found to undergo a transition to a crystalline phase above 6 GPa at room temperature from in situ, angle-dispersive, x-ray-diffraction measurements. There was no evidence of amorphization, although this phase is poorly crystallized. Hydrostatic conditions play an important role in the crystallization process. The crystal structure of this high-pressure form of ${\mathrm{GeO}}_{2}$ was found to be monoclinic, space group ${P2}_{1}/c,$ $Z=6$ and is built up of $3\ifmmode\times\else\texttimes\fi{}2$ kinked chains of edge-sharing ${\mathrm{GeO}}_{6}$ octahedra. This phase is 45% denser than \ensuremath{\alpha}-quartz-type ${\mathrm{GeO}}_{2}$ and 1% less dense than the rutile-type phase and is metastable from ambient pressure up to at least 50 GPa at room temperature. Upon heating this monoclinic phase at pressures up to 22 GPa, rutile-type ${\mathrm{GeO}}_{2}$ is formed, whereas at 43 GPa a mixture of the ${\mathrm{CaCl}}_{2}$-type and ${\mathrm{Fe}}_{2}\mathrm{N}$-type phases is obtained.

Transition to a crystalline high-pressure phase in α-GeO 2 at room temperature

Studies at extreme pressures and temperatures are helpful for understanding the physical properties of the solid state, including such classes of materials as semiconductors, superconductors or minerals. This is connected with the opportunity of tuning the pressure by many orders of magnitude. Diamond-anvil and large-anvil pressure cells installed at dedicated synchrotron beamlines are efficient tools for examination of crystal structure, equation of state, compressibility and phase transitions. One of basic methods in such studies is powder diffraction. This review is devoted to methods of powder X-ray diffraction at high-pressures generated by devices installed at synchrotron radiation sources, in particular to the principles of operation of high-pressure–high-temperature cells. General information on high-pressure diffraction facilities installed at 11 synchrotron storage rings in the world is provided. Measurement aspects are considered, including (i) pressure generation and calibration, (ii) strain in the sample, the pressure marker and the pressure-transmitting medium and (iii) pressure and temperature distributions within the cells. Sources of interest in high-pressure diffraction studies (design of new materials, observation of new phenomena, confrontation of theory with experiment) are briefly discussed. Recent developments of high-pressure methods make that pressure becomes a variable playing a key role in investigation of condensed matter. The paper ends with some remarks on the possible future developments of the technique.

High-pressure powder X-ray diffraction at the turn of the century

Abstract α-Quartz and its homeotypes are of great importance for both materials and Earth sciences. The properties of these materials depend strongly on their crystal structures and particularly the intertetrahedral bridging angle and the tetrahedral tilt angle. These angles are highly dependent on composition and the external parameters pressure and temperature. The behavior of the eleven known α-quartz homeotypes, along with examples of α-quartz-type solid solutions, are compared. The distortion in α-quartz-type structures decreases as a function of temperature and increases as a function of pressure. Thermal stability depends on initial structural distortion and on the electronic configuration of the cation. Pressure stability also depends on the former and on cation size. Transitions to new crystalline and/or amorphous forms, often with increased cation coordination number, are commonly observed at high-pressure. The combined use of high-pressure and high-temperature can be used to synthesize novel α-quartz homeotypes in compounds with small cations.

The effects of pressure, temperature and composition on the crystal structures of α-quartz homeotypes

X-ray absorption spectroscopy in mineralogy: Theory and experiment in the XANES region

High-pressure Raman scattering from GaPO4

Combined x-ray absorption spectroscopy (XAS) and x-ray diffraction experiments (EDX) on powders, both in the dispersive mode, may enable the determination of structural parameters as a function of pressure. After phase transitions, it may even be possible to determine the structure of the high pressure phases. The EDX enables the determination of the cell parameters, and eventually the space group from the systematic extinctions. On the other hand, the XAS provides information on the local environment of an atomic species, i.e., the coordination number and the first (eventually even second) neighbour distances with a high precision. The combination of these two techniques has been successfully used to determine the high pressure structure of ZnTe and HgTe. We present here recent results obtained on the high pressure properties of chalcopyrites and of berlinites. Finally, recent developments and future possibilities with the new synchrotron sources are presented.

Combined energy dispersive x-ray absorption and diffraction under high pressure

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

T. Tinoco

Author Tools

Chat about Author

Papers

Combined energy dispersive x-ray absorption and diffraction under high pressure