scholarly journals Synthesis of Paracrystalline Diamond

2021 ◽  
Author(s):  
Howard Sheng ◽  
Hu Tang ◽  
Xiaohong Yuan ◽  
Yong Cheng ◽  
Hongzhan Fei ◽  
...  
Keyword(s):  
Long Range ◽  
Amorphous Materials ◽  
Nearest Neighbor ◽  
Structural Characteristics ◽  
Range Order ◽  
Dynamics Simulation ◽  
X Ray Diffraction ◽  
Transmission Microscopy ◽  
Nucleation Sites ◽  
High Pressure High Temperature

Abstract Solids in nature can be generally classified into crystalline and non-crystalline states, depending on whether long-range lattice periodicity is present in the material. The differentiation of the two states, however, could face fundamental challenges if the degree of long-range order in crystals is significantly reduced. Here we report a unique paracrystalline state of diamond that is distinct from either crystalline or amorphous diamond. The paracrystalline diamond reported in this work, consisting of sub-nanometer-sized paracrystals that possess a well-defined crystalline medium-range order up to a few atomic shells, was synthesized in high-pressure high-temperature conditions (e.g., 30 GPa, 1600 K) employing fcc-C60 as a precursor. The structural characteristics of paracrystalline diamond was identified through a combination of X-ray diffraction, high-resolution transmission microscopy, and advanced molecular dynamics simulation. The formation of paracrystalline diamond is a result of densely distributed nucleation sites developed in compressed C60 as well as pronounced second-nearest-neighbor short-range order in amorphous diamond due to strong sp3 bonding. The discovery of paracrystalline diamond adds a new diamond form to the enriched carbon family, which exhibits distinguishing physical properties and can be furthered exploited to develop new materials. Furthermore, this work reveals the missing link in the length-scale between amorphous and crystalline states across the structural landscape, which has profound implications for recognizing complex structures arising from amorphous materials.

Fluctuation Microscopy: A New Class of Microscopy Techniques for Probing Medium Range Order in Amorphous Materials

1998 ◽  
Vol 4 (S2) ◽  
pp. 702-703
Author(s):  
J. M. Gibson ◽  
M. M. J. Treacy ◽  
P. M. Voyles
Keyword(s):  
Long Range ◽  
Short Range ◽  
Amorphous Materials ◽  
Short Range Order ◽  
Nearest Neighbor ◽  
Range Order ◽  
Regular Tetrahedron ◽  
Long Range Order ◽  
Medium Range Order ◽  
Medium Range

Amorphous materials are devoid of periodic long range order, but at the nearest-neighbor level they possess a high degree of short-range order. In amorphous tetrahedral semiconductors, such as Si and Ge, this short-range order arises because each atom attempts to satisfy four bonds arranged as a regular tetrahedron. It is the rotations about each bond, from the second-nearest-neighbor outwards, that result in the loss of long-range order. It is apparent from modeling of amorphous materials, that there is considerable flexibility as to how rapidly the medium-range-order diminishes. The continuous random network (CRN) is a hypothetical tetrahedral extended structure wherein the atoms possess full four-connected coordination, but have minimal medium-range order. However, real amorphous materials infrequently exhibit true CRN-like topologies. Traditionally, diffraction has been used to study short- and medium-range order in amorphous materials. Assuming kinematical scattering, and that every atom has a similar environment, a radial distribution function (RDF) can be extracted which is sensitive only to the averaged atom pair-correlations out to ∼1 nm.

The high-pressure cadmium borate Cd6B22O39·H2O

2015 ◽  
Vol 70 (3) ◽  
pp. 183-190 ◽  
Author(s):  
Gerhard Sohr ◽  
Nina Ciaghi ◽  
Klaus Wurst ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure High Temperature ◽  
Cell Dimensions ◽  
Temperature Experiment ◽  
Unit Cell Dimensions ◽  
Ir And Raman

AbstractSingle crystals of the hydrous cadmium borate Cd6B22O39·H2O were obtained through a high-pressure/high-temperature experiment at 4.7 GPa and 1000 °C using a Walker-type multianvil apparatus. CdO and partially hydrolyzed B2O3 were used as starting materials. A single crystal X-ray diffraction study has revealed that the structure of Cd6B22O39·H2O is similar to that of the type M6B22O39·H2O (M=Fe, Co). Layers of corner-sharing BO4 groups are interconnected by BO3 groups to form channels containing the metal cations, which are six- and eight-fold coordinated by oxygen atoms. The compound crystallizes in the space group Pnma (no. 62) [R1=0.0379, wR2=0.0552 (all data)] with the unit cell dimensions a=1837.79(5), b=777.92(2), c=819.08(3) pm, and V=1171.00(6) Å3. The IR and Raman spectra reflect the structural characteristics of Cd6B22O39·H2O.

ABSENCE OF PHASE TRANSITIONS ON TREE STRUCTURES

1993 ◽  
Vol 07 (29n30) ◽  
pp. 1947-1950 ◽  
Author(s):  
RAFFAELLA BURIONI ◽  
DAVIDE CASSI
Keyword(s):  
Long Range ◽  
Nearest Neighbor ◽  
Linear Chain ◽  
Mean Field ◽  
Range Order ◽  
The Other ◽  
Long Range Order ◽  
Field Phase ◽  
Tree Structures ◽  
Bethe Lattices

We rigorously prove that the correlation functions of any statistical model having a compact transitive symmetry group and nearest-neighbor interactions on any tree structure are equal to the corresponding ones on a linear chain. The exponential decay of the latter implies the absence of long-range order on any tree. On the other hand, for trees with exponential growth such as Bethe lattices, one can show the existence of a particular kind of mean field phase transition without long-range order.

scholarly journals Zur Darstellung und Kristallstruktur von β-NbO2 / Synthesis and Crystal Structure of β-NbO2

1982 ◽  
Vol 37 (11) ◽  
pp. 1361-1368 ◽  
Author(s):  
H.-J. Schweizer ◽  
Reginald Gruehn
Keyword(s):  
Crystal Structure ◽  
Long Range ◽  
Chemical Transport ◽  
Range Order ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
X Ray ◽  
Lattice Constants

By using chemical transport reactions with various transporting agents (HgCl2, NbCl5, Nb3O7Cl) a slightly substoiehiometric NbO2-phase, β-NbO2, was obtained from samples with O/Nb ∼ 1.5 (source; T > 1373 K) and with deposition temperatures > 1273 K (sink). The rango of composition of β-NbO2 was found to exist from NbO1.990 to NbO1.998.The structure of the tetragonal, column-shaped black crystals was determined by X-ray diffraction. It crystallizes tetragonally in the space group I41 with lattice constants a = 9.693(3) Å, c = 5.985(1) Å and Z = 10 formula units.The crystal structure of β-NbO2 is shown to be a deformed rutile type. As in α-NbO2 the Nb-atoms are grouped in pairs. However, both oxides are different with respect to their long-range order.

Anomalous x-ray diffraction measurements of long-range order in (001)-texturedL10FePtCu thin films

2012 ◽  
Vol 86 (2) ◽  
Author(s):  
M. Maret ◽  
C. Brombacher ◽  
P. Matthes ◽  
D. Makarov ◽  
N. Boudet ◽  
...  
Keyword(s):  
Thin Films ◽  
Long Range ◽  
Range Order ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
X Ray

Measurement of Long Range Order in the γ’ Phase of Nickel-Base Superalloys

1969 ◽  
Vol 13 ◽  
pp. 598-608
Author(s):  
J.R. Mihalisin
Keyword(s):  
High Temperature ◽  
Long Range ◽  
Range Order ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
High Temperature Heat Treatment ◽  
Heat Treated ◽  
Temperature Heat ◽  
Long Time ◽  
Nickel Base

The long range order parameter (S) has been measured at room- temperature on the γ’ phase extracted from IN-731 and alloys 713C and 713LC by x-ray diffraction techniques. Measurements were obtained from specimens of IN-731 and alloy 713LC in the as-cast condition and after long time rupture testing. The alloy 713 c specimens were in the as-cast and high temperature heat treated conditions.It was found that long range order in the γ’ phase of IN-731 and alloy 713LC was changed very little after long time rupture testing, and after high temperature heat treatment in the case of alloy 713C.

High-Resolution Small-Angle X-Ray Diffraction Study of Long-Range Order in Hard-Sphere Colloidal Crystals

2002 ◽  
Vol 88 (20) ◽  
Author(s):  
A. V. Petukhov ◽  
D. G. A. L. Aarts ◽  
I. P. Dolbnya ◽  
E. H. A. de Hoog ◽  
K. Kassapidou ◽  
...  
Keyword(s):  
High Resolution ◽  
Diffraction Study ◽  
Long Range ◽  
Small Angle ◽  
Hard Sphere ◽  
Colloidal Crystals ◽  
Range Order ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
X Ray

Characterization of Interfacial Structure of InGaAs/InP Short Period Superlattices by Raman Scattering and High Resolution X-Ray Diffraction

1993 ◽  
Vol 324 ◽  
Author(s):  
Teruo Mozume
Keyword(s):  
Raman Scattering ◽  
Long Range ◽  
Range Order ◽  
Interfacial Structure ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gas Source ◽  
Short Period ◽  
Short Period Superlattices

AbstractThe x-ray diffraction (XRD) of InGaAs/InP short-period superlattices (SPSL's) grown on (001)InP substrates by gas source molecular beam epitaxy (GSMBE) and by gas source migration enhanced epitaxy (GSMEE) shows that the GSMBE grown SPSL is strain free, and that GSMEE grown SPSL's with InGa-P and In-As heterointerfaces have strain-induced zerothorder satellite peak shift consistent with that in simulation results for the InGaAs/InP SPSL with one monolayer of InGaP and InAs inserted in each interface. Partial destruction of the long-range order is confirmed by the observation of the extra diffraction peak in GSMBE grown SPSL and by weak intensity of satellite peaks and nonuniform spacing between satellite peaks in GSMEE grown SPSL's. Raman scattering shows that the strain is accommodated in the interface layer in GSMEE grown samples. A confinement model without interface disorder fits the GaAs LO phonon very well. These results indicate that the local atomic arrangements are tailored by GSMEE, but that long range-order is impaired by the misfit dislocations in GSMEE grown SPSL's and by the exchange between As to P at the interfaces in GSMBE grown SPSL.

Sign in / Sign up

Export Citation Format

Share Document