المؤلفون: Quan Li, Xinxin Zhang, Yu Zhao, Taimin Cheng, Hui Chen, Guo-liang Yu

المصدر: Physical Chemistry Chemical Physics. 23:3087-3092

مصطلحات موضوعية: Materials science, General Physics and Astronomy, Diamond, 02 engineering and technology, engineering.material, Electron deficiency, 021001 nanoscience & nanotechnology, 01 natural sciences, Electron localization function, Chemical physics, Covalent bond, Phase (matter), 0103 physical sciences, Vickers hardness test, Superhard material, engineering, Physical and Theoretical Chemistry, 010306 general physics, 0210 nano-technology, Ternary operation

الوصف: B2CN was one of the synthesized light element compounds, which was expected to be superhard material with a metallic character due to its electron deficienct nature. However, in this work, we discovered two novel semiconducting superhard B2CN phases using particle swarm intelligence technique and first-principles calculations, which were reported to have three-dimensional and four coordinated covalent diamond-like structures. These two new phases were calculated to be dynamically stable at zero and high pressures, and can be deduced from the previously reported Pmma phase by pressure-induced structural phase transitions. More importantly, unlike the previously proposed metallic B2CN structures, these two new phases combine superhard (the calculated Vickers hardness reached ∼55 GPa) and semiconducting character. The semiconducting behavior of the newly predicted B2CN phases breaks the traditional view of the metallic character of the electron deficient diamond-like B-C-N ternary compounds. By a detail analyzation of the electron localization functions of these two new phases, three-center bonds were reported between some B, C and B atoms, which were suggested to be the primary mechanism that helps the compound overcome its electron-deficient nature and finally exhibit a semiconducting behavior.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::a5b0925353edf5a7f9cc2936a60b80daTest
https://doi.org/10.1039/d0cp05793bTest

المؤلفون: Taimin Cheng, Guo-liang Yu, Chong-Yuan Ge, Lin Li, Xinxin Zhang, Lin Zhu, Yong Su

المصدر: Journal of Magnetism and Magnetic Materials. 453:67-77

مصطلحات موضوعية: Phase transition, Materials science, Magnetic moment, Condensed matter physics, Magnetic structure, Magnetism, Magnetostriction, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, Ferromagnetism, Ferrimagnetism, 0103 physical sciences, Condensed Matter::Strongly Correlated Electrons, 010306 general physics, Spontaneous magnetization

الوصف: The ordered crystalline Invar alloy Fe3Pt is in a special magnetic critical state, under which the lattice dynamic stability of the system is extremely sensitive to external pressures. We studied the pressure dependence of enthalpy and magnetism of Fe3Pt in different crystalline alloys by using the first-principles projector augmented-wave method based on the density functional theory. Results show that the P4/mbm structure is the ground state structure and is more stable relative to other structures at pressures below 18.54 GPa. The total magnetic moments of L12, I4/mmm and DO22 structures decrease rapidly with pressure and oscillate near the ferromagnetic collapse critical pressure. At the pressure of 43 GPa, the ferrimagnetic property in DO22 structure becomes apparently strengthened and its volume increases rapidly. The lattice dynamics calculation for L12 structures at high pressures shows that the spontaneous magnetization of the system in ferromagnetic states induces the softening of the transverse acoustic phonon TA1 (M), and there exists a strong spontaneous volume magnetostriction at pressures below 26.95 GPa. Especially, the lattice dynamics stability is sensitive to pressure, in the pressure range between the ferromagnetic collapse critical pressure (41.9 GPa) and the magnetism completely disappearing pressure (57.25 GPa), and near the pressure of phase transition from L12 to P4/mbm structure (27.27 GPa). Moreover, the instability of magnetic structure leads to a prominent elastic modulus oscillation, and the spin polarizability of electrons near the Fermi level is very sensitive to pressures in that the pressure range. The pressure induces the stability of the phonon spectra of the system at pressures above 57.25 GPa.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::93a810f40c816ff084aba47913b5c417Test
https://doi.org/10.1016/j.jmmm.2018.01.008Test

المؤلفون: Guo-liang Yu, Yong Su, Lin Li, Lin Zhu, Tai-Min Cheng

المصدر: Journal of Magnetism and Magnetic Materials. 451:87-95

مصطلحات موضوعية: Phase transition, Materials science, Condensed matter physics, Magnetic moment, Magnetism, Phonon, Alloy, 02 engineering and technology, engineering.material, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, Ferromagnetism, Lattice (order), 0103 physical sciences, engineering, Condensed Matter::Strongly Correlated Electrons, 010306 general physics, 0210 nano-technology, Spontaneous magnetization

الوصف: The stability of lattice dynamics and the magnetism of the ordered γ′-Fe4N crystalline alloy at high pressures were studied by first-principle calculations based on density-functional theory. The dynamical stable new phase P2/m-Fe4N at high pressures was found by conducting the softening phenomenon at the point M (0.5 0.5 0) of the acoustic phonon at 10 GPa in the γ′-Fe4N via soft-mode phase transition theory. Compared to the phonon spectrum of γ′-Fe4N without considering electronic spin polarization, the ground-state lattice dynamical stability of the ferromagnetic phase γ′-Fe4N is induced by the spontaneous magnetization at pressures below 1 GPa. However, P2/m-Fe4N is more thermodynamically stable than γ′-phase at pressures below 1 GPa, and the magnetic moments of the two phases are almost the same. The ground-state structure of P2/m phase is more stable than that of γ′-phase in the pressure range from 2.9 to 19 GPa. The magnetic moments of the two phases are almost the same in the pressure range from 20 to 214 GPa, but the ground-state structure of γ′-phase is more stable than that of P2/m phase in the pressure range from 143.8 to 214 GPa. On the contrary, the ground-state structure of P2/m phase is more stable when the pressure is above 214 GPa. In the pressure range from 214 to 300 GPa, the magnetic moment of P2/m phase is lower than that of γ′-phase, and the magnetic moments of the two phase tend to be consistent when the pressure exceeds 300 GPa.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::59b3d817a6466b46a9305e7a55509a83Test
https://doi.org/10.1016/j.jmmm.2017.09.086Test

المؤلفون: Taimin Cheng, Yu Zhao, Xinxin Zhang, Guo-liang Yu, Quan Li

المصدر: Journal of Alloys and Compounds. 854:157255

مصطلحات موضوعية: Materials science, Phonon, Mechanical Engineering, Enthalpy, Metals and Alloys, Particle swarm optimization, 02 engineering and technology, Boron carbide, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Stability (probability), 0104 chemical sciences, Characterization (materials science), Condensed Matter::Materials Science, chemistry.chemical_compound, chemistry, Mechanics of Materials, Chemical physics, Superhard material, Materials Chemistry, 0210 nano-technology, Dispersion (chemistry)

الوصف: B4N is expected to be a superhard material with outstanding mechanical properties like B4C. The longstanding uncertainty in its stable structural information impeded the understanding of its physical and chemical properties. Here, we systematically investigated the thermodynamically stable phases of B4N and their corresponding functional properties by using the particle swarm optimization method combined with first-principles calculations. Two new icosahedra-based B4N phases that different from the rhombohedral boron carbide type structure were predicted to be more thermodynamically stable in the pressure range of 0–300 GPa. Their dynamical stability has been identified by the theoretical phonon dispersion curves. By contrast, the long-assumed rhombohedral boron carbide type structure of B4N was currently determined to have much higher formation enthalpy and large imaginary phonon branches at zero pressure. As a result, it is obviously less stable than the newly predicted two phases. The calculated electrical and mechanical properties of these two new phases show that they possess both metallic and superhard characters, which will stimulate further high-pressure studies on synthesis and characterization.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::62640355c1d561a1ecfb8656fdfa9f16Test
https://doi.org/10.1016/j.jallcom.2020.157255Test

المؤلفون: Guo-liang Yu, Zhi-rui Cheng, Taimin Cheng, Xinxin Zhang

المصدر: Computational Materials Science. 188:110168

مصطلحات موضوعية: Phase transition, Materials science, General Computer Science, Condensed matter physics, Magnetic moment, Phonon, Alloy, Enthalpy, General Physics and Astronomy, 02 engineering and technology, General Chemistry, Crystal structure, engineering.material, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Condensed Matter::Materials Science, Computational Mathematics, Ferromagnetism, Mechanics of Materials, engineering, General Materials Science, Orthorhombic crystal system, 0210 nano-technology

الوصف: FePd crystalline alloy with chemical stoichiometry of 1:1 is important permanent magnets and ultrahigh magnetic recording material, however there is few reports on its stable crystal structures under normal and high pressures. Thus, the stable crystal structures of FePd alloy were explored here by using particle swarm optimization algorithm and the soft-mode phase transition theory. Four new phases of FePd were discovered, namely, Imma, Cmmm-I, Cmmm-П, and P4/nmm. The structure, magnetisim, elasticity and lattice dynamics of the system were systematically investigated by first-principles calculations. It was found that the ferromagnetic state of these structures is more energetically favorable than the non-magnetic state below their respective critical pressure of ferromagnetic collapse. The phonon dispersion curves have no imaginary frequency and elastic constants fulfill Born’s criteria demonstrated that these four structures are dynamically and mechanically stable at pressure range of 0 to 59.1 GPa. These four new phases were found have negative formation enthalpy and the three orthorhombic structures were identified to be meta-stable in the pressure range of 0 to 59.1 GPa since they possess very small enthalpy difference which could not be firmly distinguished by our calculations relative to the experimentally known L10 phase. After 59.1 GPa, P4/nmm structure became the energetically most stable structure accompanied by simultaneous collapse of magnetic moments and lattice volume. The underlying mechanism was analyzed and attributed to be the simultaneously collapse of magnetoelastic force of Fe-Fe.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::4e07cd888d3a26ad5dda58008de767daTest
https://doi.org/10.1016/j.commatsci.2020.110168Test

المؤلفون: Xinxin Zhang, Wei-Jiang Gong, Guo-liang Yu, Taimin Cheng

المصدر: Journal of Magnetism and Magnetic Materials. 510:166904

مصطلحات موضوعية: 010302 applied physics, Materials science, Magnetic moment, Condensed matter physics, Magnetism, Phonon, Alloy, 02 engineering and technology, engineering.material, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, Ferromagnetism, 0103 physical sciences, engineering, Condensed Matter::Strongly Correlated Electrons, Elasticity (economics), 0210 nano-technology, Ground state, Spontaneous magnetization

الوصف: We have systematically explored the pressure dependence of magnetism, electronic structure, elasticity and lattice dynamics of the ferromagnetic L10-FePd crystalline alloy by employing first-principles calculations. All predicted properties of the ground state are well consistent with available experimental and theoretical results. The total magnetic moment decreases slowly with pressure before the ferromagnetic collapse critical pressure of about 164 GPa and then sharply decreases near the 164 GPa, and the (C44-C66) value changed from positive to negative. The phonon dispersion relations and phonon densities of state are also investigated at zero and high pressures. Owing to the spontaneous magnetization of the system, the ferromagnetic L10-FePd crystalline alloy is dynamically stable at pressures below 171 GPa (above which the magnetism completely disappears). When the pressure was greater than 171.4 GPa, the system dynamics became unstable. The calculated elastic properties indicate that the L10-FePd alloy is mechanically stable up to 180 GPa. The ferromagnetic L10-FePd crystalline alloy has good ductility and metallicity outside the ferromagnetic collapse pressure region, but the L10-FePd crystalline alloy has an abnormal phenomenon of a sudden sharp increase in brittleness near 162 GPa. We found this anomaly from the Pugh ratio B/G and Poisson's ratio of the system and the change of Cauchy pressures (C12-C66) and (C13-C44) with pressure, and this anomaly was analyzed with compression factor and magnetoelastic force.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::04a1a2cd5e8c1f414bf8a2df5cdc18d9Test
https://doi.org/10.1016/j.jmmm.2020.166904Test

المؤلفون: Guo-Liang Yu, Zhi-Gang Wang

المصدر: Chinese Physics C. 44:033103

مصطلحات موضوعية: Physics, Nuclear and High Energy Physics, Meson, 010308 nuclear & particles physics, FOS: Physical sciences, Order (ring theory), Astronomy and Astrophysics, 01 natural sciences, Combinatorics, High Energy Physics - Phenomenology, High Energy Physics - Phenomenology (hep-ph), Excited state, 0103 physical sciences, B meson, 010306 general physics, Instrumentation

الوصف: In order to make a further confirmation of the assignments of the excited bottom and bottom-strange mesons , , and and identify possible assignments of and , we study the strong decay of these states with the decay model. Our analysis supports the assignments of and as the and states, and and as the strange partners of and . Besides, we tentatively identify the recently observed and as the and states. It is noted that these conclusions need further confirmation by measurements of the decay channels and .

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::ef6c56d484877005efcb83910429622eTest
https://doi.org/10.1088/1674-1137/44/3/033103Test

المؤلفون: Zhen Yu Li, Zhi-Gang Wang, Guo Liang Yu

المصدر: Physical Review D. 94

مصطلحات موضوعية: Nuclear physics, Physics, Particle physics, Meson, 010308 nuclear & particles physics, High Energy Physics::Phenomenology, 0103 physical sciences, High Energy Physics::Experiment, Nuclear Experiment, 010306 general physics, 01 natural sciences

الوصف: In this work, we systematically study the strong decay behavior of the charmed mesons ${D}_{1}^{*}(2680)$, ${D}_{3}^{*}(2760)$, and ${D}_{2}^{*}(3000)$ reported by the LHCb Collaboration. By comparing the masses and the decay properties with the results of the experiment, we assign these newly observed mesons as the $2S\frac{1}{2}{1}^{\ensuremath{-}}$, $1D\frac{5}{2}{3}^{\ensuremath{-}}$, and $1F\frac{5}{2}{2}^{+}$ states, respectively. As a byproduct, we also study the strong decays of the unobserved $2P\frac{3}{2}{2}^{+}$, $2F\frac{5}{2}{2}^{+}$, and $3P\frac{3}{2}{2}^{+}$ charmed mesons, which is useful for future experiments in searching for these charmed mesons.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::5f938cf55eddcb4cef905aea54118232Test
https://doi.org/10.1103/physrevd.94.074024Test

المؤلفون: Zun-Yan Di, Zhi-Gang Wang, Guo-Liang Yu

المصدر: Communications in Theoretical Physics. 71:685

مصطلحات موضوعية: Physics, Quantum chromodynamics, Particle physics, QCD sum rules, Physics and Astronomy (miscellaneous), 010308 nuclear & particles physics, 01 natural sciences, Pseudoscalar, 0103 physical sciences, Bound state, Molecule, 010306 general physics, Energy (signal processing), Bar (unit)

الوصف: In this article, we assume that there exist the pseudoscalar D D ¯ s 0 * ( 2317 ) and D * D ¯ s 1 * ( 2460 ) molecular states Z1,2 and construct the color singlet-singlet molecule-type interpolating currents to study their masses with the QCD sum rules. In calculations, we consider the contributions of the vacuum condensates up to dimension-10 and use the formula μ = M X / Y / Z 2 − ( 2 M c ) 2 to determine the energy scales of the QCD spectral densities. The numerical results, M Z 1 = 4.61 − 0.08 + 0.11 GeV and M Z 2 = 4.60 − 0.06 + 0.07 GeV , which lie above the D D ¯ s 0 * ( 2317 ) and D * D ¯ s 1 * ( 2460 ) thresholds respectively, indicate that the D D ¯ s 0 * ( 2317 ) and D * D ¯ s 1 * ( 2460 ) are difficult to form bound state molecular states, the Z1,2 are probably resonance states.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::4ec5003cae46570dbc1ad4bc2914158aTest
https://doi.org/10.1088/0253-6102/71/6/685Test

المؤلفون: Rong-Hua Guan, Guo-Liang Yu, Zhi-Gang Wang

المصدر: International Journal of Modern Physics A. 32:1750203

مصطلحات موضوعية: Nuclear and High Energy Physics, Particle physics, Dirac (software), Structure (category theory), 01 natural sciences, Combinatorics, 0103 physical sciences, Computer Science::General Literature, 010306 general physics, ComputingMilieux_MISCELLANEOUS, Coupling constant, Physics, QCD sum rules, 010308 nuclear & particles physics, Computer Science::Information Retrieval, Form factor (quantum field theory), Astrophysics::Instrumentation and Methods for Astrophysics, Computer Science::Computation and Language (Computational Linguistics and Natural Language and Speech Processing), Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Baryon, Charmed baryons, TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Strong coupling, Analytic function

الوصف: The strong coupling constants not only are important to understand the strong interactions of the heavy baryons, but can also help us reveal the nature and structure of these baryons. Additionally, researchers indeed have made great efforts to calculate some of the strong coupling constants, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], etc. In this paper, we analyze the strong vertices [Formula: see text] and [Formula: see text] using the three-point QCD sum rules under the Dirac structure of [Formula: see text]. We perform our analysis by considering the contributions of the perturbative part and the condensate terms of [Formula: see text] and [Formula: see text]. After the form factors are calculated, they are then fitted into analytical functions which are used to get the strong coupling constants for these two vertices. The final results are [Formula: see text] and [Formula: see text].

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::82050f454662c620e2a836d4ae76a7dcTest
https://doi.org/10.1142/s0217751x17502037Test