The Experts below are selected from a list of 2622 Experts worldwide ranked by ideXlab platform
Hui Wang - One of the best experts on this subject based on the ideXlab platform.
-
twofold coordinated ground state and eightfold high pressure phases of heavy transition metal nitrides mn2 m os ir ru and rh
Inorganic Chemistry, 2009Co-Authors: Yinwei Li, Hui Wang, Quan LiAbstract:Using ab initio evolutionary methodology for crystal structure prediction, a twofold coordinated ground-state hexagonal structure (P6/mmm, 1 f.u./cell) with peculiar double N═N bonded N2 units was uncovered for MN2 (M = Os, Ir, Ru, and Rh) compounds. This structure exhibits an unusual incompressibility along the c axis, higher than that of diamond. At much higher pressures, an eightfold coordinated tetragonal structure (P4/mbm, 2 f.u./cell) containing MN8 cuboids was unraveled and possesses also orientational ultra-incompressibility. A unified phase transition diagram for these nitrides was thus derived to reveal the intriguing chemistry of nitrogen at extreme conditions. Formation energy calculations demonstrate that the ground state phase is synthesizable at low pressure (∼40 GPa) while the eightfold phase can be achieved through the phase transformation via the Marcasite structure.
-
twofold coordinated ground state and eightfold high pressure phases of heavy transition metal nitrides mn2 m os ir ru and rh
Inorganic Chemistry, 2009Co-Authors: Hui Wang, Tian Cui, Guangtian ZouAbstract:Using ab initio evolutionary methodology for crystal structure prediction, a twofold coordinated ground-state hexagonal structure (P6/mmm, 1 f.u./cell) with peculiar double N horizontal lineN bonded N(2) units was uncovered for MN(2) (M = Os, Ir, Ru, and Rh) compounds. This structure exhibits an unusual incompressibility along the c axis, higher than that of diamond. At much higher pressures, an eightfold coordinated tetragonal structure (P4/mbm, 2 f.u./cell) containing MN(8) cuboids was unraveled and possesses also orientational ultra-incompressibility. A unified phase transition diagram for these nitrides was thus derived to reveal the intriguing chemistry of nitrogen at extreme conditions. Formation energy calculations demonstrate that the ground state phase is synthesizable at low pressure ( approximately 40 GPa) while the eightfold phase can be achieved through the phase transformation via the Marcasite structure.
Quan Li - One of the best experts on this subject based on the ideXlab platform.
-
twofold coordinated ground state and eightfold high pressure phases of heavy transition metal nitrides mn2 m os ir ru and rh
Inorganic Chemistry, 2009Co-Authors: Yinwei Li, Hui Wang, Quan LiAbstract:Using ab initio evolutionary methodology for crystal structure prediction, a twofold coordinated ground-state hexagonal structure (P6/mmm, 1 f.u./cell) with peculiar double N═N bonded N2 units was uncovered for MN2 (M = Os, Ir, Ru, and Rh) compounds. This structure exhibits an unusual incompressibility along the c axis, higher than that of diamond. At much higher pressures, an eightfold coordinated tetragonal structure (P4/mbm, 2 f.u./cell) containing MN8 cuboids was unraveled and possesses also orientational ultra-incompressibility. A unified phase transition diagram for these nitrides was thus derived to reveal the intriguing chemistry of nitrogen at extreme conditions. Formation energy calculations demonstrate that the ground state phase is synthesizable at low pressure (∼40 GPa) while the eightfold phase can be achieved through the phase transformation via the Marcasite structure.
Guangtian Zou - One of the best experts on this subject based on the ideXlab platform.
-
twofold coordinated ground state and eightfold high pressure phases of heavy transition metal nitrides mn2 m os ir ru and rh
Inorganic Chemistry, 2009Co-Authors: Hui Wang, Tian Cui, Guangtian ZouAbstract:Using ab initio evolutionary methodology for crystal structure prediction, a twofold coordinated ground-state hexagonal structure (P6/mmm, 1 f.u./cell) with peculiar double N horizontal lineN bonded N(2) units was uncovered for MN(2) (M = Os, Ir, Ru, and Rh) compounds. This structure exhibits an unusual incompressibility along the c axis, higher than that of diamond. At much higher pressures, an eightfold coordinated tetragonal structure (P4/mbm, 2 f.u./cell) containing MN(8) cuboids was unraveled and possesses also orientational ultra-incompressibility. A unified phase transition diagram for these nitrides was thus derived to reveal the intriguing chemistry of nitrogen at extreme conditions. Formation energy calculations demonstrate that the ground state phase is synthesizable at low pressure ( approximately 40 GPa) while the eightfold phase can be achieved through the phase transformation via the Marcasite structure.
Masashi Hasegawa - One of the best experts on this subject based on the ideXlab platform.
-
Highly Coordinated Iron and Cobalt Nitrides Synthesized at High Pressures and High Temperatures
2017Co-Authors: Ken Niwa, Toshiki Terabe, Daiki Kato, Shin Takayama, Masahiko Kato, Kazuo Soda, Masashi HasegawaAbstract:Highly coordinated iron and cobalt nitrides were successfully synthesized via direct chemical reaction between a transition metal and molecular nitrogen at pressures above approximately 30 GPa using a laser-heated diamond anvil cell. The synthesized novel transition metal nitrides were found to crystallize into the NiAs-type or Marcasite-type structure. NiAs-type FeN could be quenched at ambient pressure, although it was gradually converted to the ZnS-type structure after the pressure was released. On the other hand, CoN was recovered with ZnS-type structure through a phase transition from NiAs-type structure at approximately a few gigapascals during decompression. Marcasite-type CoN2 was also synthesized at pressures above approximately 30 GPa. High-pressure in situ X-ray diffraction measurement showed that the zero-pressure bulk modulus of Marcasite-type CoN2 is 216(18) GPa, which is comparable to that of RhN2. This indicates that the interatomic distance of the N–N dimer in Marcasite-type CoN2 is short because of weak orbital interaction between cobalt and nitrogen atoms, as in RhN2. Surprisingly, a first-principles electronic band calculation suggests that the NiAs-type FeN and CoN and Marcasite-type CoN2 exhibit metallic characteristics with magnetic moments of 3.4, 0.6, and 1.2 μB, respectively. The ferromagnetic NiAs-type structure originates from the anisotropic arrangement of transition atoms stacked along the c axis
-
high pressure synthesis of Marcasite type rhodium pernitride
ChemInform, 2014Co-Authors: Ken Niwa, Dmytro Dzivenko, Kentaro Suzuki, Ralf Riedel, Ivan Troyan, M I Eremets, Masashi HasegawaAbstract:RhN2 is prepared by high temperature/high-pressure reaction of Rh and N2 (IR laser-heated diamond anvil cell, 43.2 GPa, ≈3000 K).
-
high pressure synthesis of Marcasite type rhodium pernitride
Inorganic Chemistry, 2014Co-Authors: Ken Niwa, Dmytro Dzivenko, Kentaro Suzuki, Ralf Riedel, Ivan Troyan, M I Eremets, Masashi HasegawaAbstract:Marcasite-type rhodium nitride was successfully synthesized in a direct chemical reaction between a rhodium metal and molecular nitrogen at 43.2 GPa using a laser-heated diamond-anvil cell. This material shows a low zero-pressure bulk modulus of K0 = 235(13) GPa, which is much lower than those of other platinum group nitrides. This finding is due to the weaker bonding interaction between metal atoms and quasi-molecular dinitrogen units in the Marcasite-type structure, as proposed by theoretical studies.
David A Fike - One of the best experts on this subject based on the ideXlab platform.
-
sulfur isotope analysis of microcrystalline iron sulfides using secondary ion mass spectrometry imaging extracting local paleo environmental information from modern and ancient sediments
Rapid Communications in Mass Spectrometry, 2019Co-Authors: Roger N Bryant, Clive Jones, M R Raven, M L Gomes, William M Berelson, Alexander S Bradley, David A FikeAbstract:Author(s): Bryant, Roger N; Jones, Clive; Raven, Morgan R; Gomes, Maya L; Berelson, William M; Bradley, Alexander S; Fike, David A | Abstract: RATIONALE:Sulfur isotope ratio measurements of bulk sulfide from marine sediments have often been used to reconstruct environmental conditions associated with their formation. In situ microscale spot analyses by secondary ion mass spectrometry (SIMS) and laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) have been utilized for the same purpose. However, these techniques are often not suitable for studying small (≤10 μm) grains or for detecting intra-grain variability. METHODS:Here, we present a method for the physical extraction (using lithium polytungstate heavy liquid) and subsequent sulfur isotope analysis (using SIMS; CAMECA IMS 7f-GEO) of microcrystalline iron sulfides. SIMS sulfur isotope ratio measurements were made via Cs+ bombardment of raster squares with sides of 20-130 μm, using an electron multiplier (EM) detector to collect counts of 32 S- and 34 S- for each pixel (128 × 128 pixel grids) for between 20 and 960 cycles. RESULTS:The extraction procedure did not discernibly alter pyrite grain-size distributions. The apparent inter-grain variability in 34 S/32 S in 1-4 μm-sized pyrite and Marcasite fragments from isotopically homogeneous hydrothermal crystals was ~ ±2‰ (1σ), comparable with the standard error of the mean for individual measurements (≤ ±2‰, 1σ). In contrast, grain-specific 34 S/32 S ratios in modern and ancient sedimentary pyrites and Marcasites can have inter- and intra-grain variability g60‰. The distributions of intra-sample isotopic variability are consistent with bulk 34 S/32 S values. CONCLUSIONS:SIMS analyses of isolated iron sulfide grains yielded distributions that are isotopically representative of bulk 34 S/32 S values. Populations of iron sulfide grains from sedimentary samples record the evolution of the S-isotopic composition of pore water sulfide in their S-isotopic compositions. These data allow past local environmental conditions to be inferred.