15 results on '"Zhuang Wang"'
Search Results
2. Model reconstructions for the Si(337) orientation
- Author
-
Feng-Chuan Chuang, Ciobanu, Cristian V., Cai-Zhuang Wang, and Kai-Ming Ho
- Subjects
Silicon compounds -- Electric properties ,Algorithms -- Analysis ,Molecular dynamics -- Research ,Algorithm ,Physics - Abstract
An investigation of the Si(337)-(2x1) reconstructions is presented to search for the most favorable atomic configuration based on a genetic algorithm, coupled with a highly optimized empirical potential (HOEP) for silicon. The findings lend support to the minimization approach adopted, thus showing that sampling the configuration space using the HOEP potential is a versatile way to find good candidate reconstructions for high-index Si surfaces.
- Published
- 2005
3. Cooling rate dependence of structural order in Al90Sm10 metallic glass.
- Author
-
Yang Sun, Yue Zhang, Feng Zhang, Zhuo Ye, Zejun Ding, Cai-Zhuang Wang, and Kai-Ming Ho
- Subjects
METALLIC glasses ,COOLING loads (Mechanical engineering) ,COOLING systems ,ALUMINUM metallurgy ,METALLIC glasses synthesis ,COOLING - Abstract
The atomic structure of Al
90 Sm10 metallic glass is studied using molecular dynamics simulations. By performing a long sub-Tg annealing, we developed a glass model closer to the experiments than the models prepared by continuous cooling. Using the cluster alignment method, we found that "3661" cluster is the dominating short-range order in the glass samples. The connection and arrangement of "3661" clusters, which define the medium-range order in the system, are enhanced significantly in the sub-Tg annealed sample as compared with the fast cooled glass samples. Unlike some strong binary glass formers such as Cu64.5 Zr35.5 , the clusters representing the short-range order do not form an interconnected interpenetrating network in Al90 Sm10 , which has only marginal glass formability. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
4. Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations.
- Author
-
Xin Zhao, Liqin Ke, Manh Cuong Nguyen, Cai-Zhuang Wang, and Kai-Ming Ho
- Subjects
COBALT alloys ,ZIRCONIUM alloys ,BORON alloys ,MAGNETS ,MAGNETIC properties of solids ,CALCULATIONS & mathematical techniques in atomic physics - Abstract
The structures and magnetic properties of Co-Zr-B alloys near the composition of Co
5 Zr with B at. % ≤6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the "Co11 Zr2 " polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the "interruption" sites. First-principles calculations showed that the magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co5 Zr phase and larger than that of the low-temperature Co5.25 Zr phase. Our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
5. Cluster expansion modeling and Monte Carlo simulation of alnico 5-7 permanent magnets.
- Author
-
Manh Cuong Nguyen, Xin Zhao, Cai-Zhuang Wang, and Kai-Ming Ho
- Subjects
ALNICOS ,MAGNETIC materials ,PERMANENT magnets ,MONTE Carlo method ,SIMULATION methods & models - Abstract
The concerns about the supply and resource of rare earth (RE) metals have generated a lot of interests in searching for high performance RE-free permanent magnets. Alnico alloys are traditional non-RE permanent magnets and have received much attention recently due their good performance at high temperature. In this paper, we develop an accurate and efficient cluster expansion energy model for alnico 5-7. Monte Carlo simulations using the cluster expansion method are performed to investigate the structure of alnico 5-7 at atomistic and nano scales. The alnico 5-7 master alloy is found to decompose into FeCo-rich and NiAl-rich phases at low temperature. The boundary between these two phases is quite sharp (∼2 nm) for a wide range of temperature. The compositions of the main constituents in these two phases become higher when the temperature gets lower. Both FeCo-rich and NiAl-rich phases are in B2 ordering with Fe and Al on α-site and Ni and Co on -site. The degree of order of the NiAl-rich phase is much higher than that of the FeCo-rich phase. A small magnetic moment is also observed in NiAl-rich phase but the moment reduces as the temperature is lowered, implying that the magnetic properties of alnico 5-7 could be improved by lowering annealing temperature to diminish the magnetism in NiAl-rich phase. The results from our Monte Carlo simulations are consistent with available experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
6. An ultra-incompressible Mn3N compound predicted by first-principles genetic algorithm
- Author
-
Feng Zhang, Cai-Zhuang Wang, Yang Sun, Chao Zhang, and Kai-Ming Ho
- Subjects
010302 applied physics ,Coupling ,Bulk modulus ,Materials science ,Condensed matter physics ,Phonon ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Manganese ,Nitride ,021001 nanoscience & nanotechnology ,01 natural sciences ,Stability (probability) ,Condensed Matter::Materials Science ,chemistry ,Condensed Matter::Superconductivity ,0103 physical sciences ,Compressibility ,Condensed Matter::Strongly Correlated Electrons ,Isostructural ,0210 nano-technology - Abstract
Using genetic algorithms for an unbiased structure search and first-principles total-energy calculations, a stable manganese nitride, Mn3N, is discovered. Mn3N is a nonmagnetic metal and isostructural to superhard Re3N. Mn3N exhibits a large bulk modulus and incompressibility comparable to that of the ultra-incompressible OsB. We show that the large bulk modulus can be attributed to the strong covalent bonding in this system. Phonon calculations and analysis confirm the dynamical stability of the Mn3N compound. We also show that weak electron–phonon coupling leads to a small superconducting transition temperature for Mn3N.
- Published
- 2020
7. Theoretical search for possible Li–Ni–B crystal structures using an adaptive genetic algorithm
- Author
-
Volodymyr Gvozdetskyi, Zijing Lin, Yang Sun, Linhan Xu, Renhai Wang, Kai-Ming Ho, Julia V. Zaikina, Feng Zhang, Xin Zhao, and Cai-Zhuang Wang
- Subjects
010302 applied physics ,Materials science ,Ternary numeral system ,Hydride ,General Physics and Astronomy ,02 engineering and technology ,Crystal structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,Octahedron ,Transition metal ,Chemical physics ,0103 physical sciences ,Density functional theory ,Isostructural ,0210 nano-technology ,Ternary operation - Abstract
The structural diversity of rare-earth and transition metal borides indicates that alkali-transition metal borides (A-T-B) show tremendous promise in exhibiting a variety of crystal structures with different dimensionalities of T-B frameworks. On the other hand, the A-T-B ternary systems are severely underexplored because of the synthetic challenges associated with their preparation. Accurate and efficient computational predictions of low-energy stable and metastable phases can identify the optimal compositions of the hypothetical compounds in the A-T-B systems to guide the synthesis. In this work, we have computationally discovered several new phases in the Li–Ni–B ternary system. The newly discovered LiNiB, Li2Ni3B, and Li2NiB phases expand the existing theoretical database, and the convex-hull surface of Li–Ni–B has been re-constructed. The lowest energy structure of the LiNiB compound has been found by an adaptive genetic algorithm with layered motif, which matches with the experimentally determined structure. According to our electrochemical calculations, LiNiB and another predicted layered Li2NiB compounds have great potential as anode materials for lithium batteries. The Li2Ni3B compound with the space group P4332 was predicted to crystallize in a cubic structure composed of distorted octahedral units of BNi6, which is isostructural to two noncentrosymmetric superconductors Li2Pd3B and Li2Pt3B. While we were unable to experimentally confirm the Li2Ni3B compound utilizing the hydride synthetic route, attempts to synthesize this compound by alternate methods remain highly desirable, considering its potential superconducting properties.
- Published
- 2020
8. Structures and magnetic properties of iron silicide from adaptive genetic algorithm and first-principles calculations
- Author
-
Zejin Yang, Fuxiang Li, Shunqing Wu, Tongqi Wen, Manh Cuong Nguyen, Xin Zhao, Ling Tang, Shu Yu, Kai-Ming Ho, and Cai-Zhuang Wang
- Subjects
Convex hull ,Condensed Matter - Materials Science ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Magnetic moment ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,Crystal structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Crystal structure prediction ,chemistry.chemical_compound ,Magnetic anisotropy ,chemistry ,Magnet ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Atom ,Silicide ,010306 general physics ,0210 nano-technology - Abstract
We performed a systematic search for low-energy structures of binary iron silicide over a wide range of compositions using the crystal structure prediction method based on adaptive genetic algorithm. 36 structures with formation energies within 50 meV/atom (11 of them are within 20 meV) above the convex hull formed by experimentally known stable structures are predicted. Magnetic properties of these low-energy structures are investigated. Some of these structures can be promising candidates for rare-earth-free permanent magnet.
- Published
- 2018
9. Cooling rate dependence of structural order in Ni62Nb38 metallic glass
- Author
-
Beilin Ye, Nan Wang, Zejin Yang, Cai-Zhuang Wang, Ling Tang, Kai-Ming Ho, Yang Sun, and Tongqi Wen
- Subjects
Materials science ,Amorphous metal ,Alloy ,General Physics and Astronomy ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Amorphous solid ,Annealing (glass) ,Molecular dynamics ,Distortion ,0103 physical sciences ,Cluster (physics) ,engineering ,Vitrification ,010306 general physics ,0210 nano-technology - Abstract
Molecular dynamics (MD) simulations are performed to study the structure of Ni62Nb38 bulk metallic glass at the atomistic level. Structural analysis based on the cluster alignment method is carried out and a new Ni-centered distorted-icosahedra (DISICO) motif is excavated. We show that the short-range order and medium-range order in the glass are enhanced with lower cooling rate. Almost 50% of the clusters around the Ni atoms in the well-annealed Ni62Nb38 glass sample from our MD simulations can be classified as DISICO. It is revealed that the structural distortion with respect to the perfect icosahedra is driven by chemical ordering in the distorted region of the DISICO motif. The relationship between the structure, energy, and dynamics in this glass-forming alloy during the cooling and annealing processes is also established.
- Published
- 2018
10. Transition metal partially supported graphene: Magnetism and oscillatory electrostatic potentials
- Author
-
Cai-Zhuang Wang and Xiaojie Liu
- Subjects
Materials science ,Nanostructure ,Magnetic moment ,Condensed matter physics ,Graphene ,Magnetism ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Transition metal ,Ferromagnetism ,law ,Ab initio quantum chemistry methods ,Electric field ,0103 physical sciences ,010306 general physics ,0210 nano-technology - Abstract
Using first-principles calculations, we show that Mn and Cr layers under graphene exhibit almost zero magnetic moment due to anti-ferromagnetic order, while ferromagnetic coupling in Fe, Co, and Ni leads to large magnetic moment. Transition metal partially supported graphene, with a mixture of supported and pristine areas, exhibits an oscillatory electrostatic potential, thus alternating the electric field across the supported and pristine areas. Such an effect can be utilized to control mass transport and nanostructure self-organization on graphene at the atomic level.
- Published
- 2017
11. Cooling rate dependence of structural order in Al90Sm10 metallic glass
- Author
-
Zhuo Ye, Yue Zhang, Feng Zhang, Yang Sun, Kai-Ming Ho, Zejun Ding, and Cai-Zhuang Wang
- Subjects
Materials science ,Amorphous metal ,Annealing (metallurgy) ,Metallurgy ,General Physics and Astronomy ,Binary number ,02 engineering and technology ,Porous glass ,021001 nanoscience & nanotechnology ,Condensed Matter::Disordered Systems and Neural Networks ,01 natural sciences ,Condensed Matter::Soft Condensed Matter ,Molecular dynamics ,0103 physical sciences ,Cluster (physics) ,Formability ,Composite material ,010306 general physics ,0210 nano-technology ,Glass transition - Abstract
The atomic structure of Al90Sm10 metallic glass is studied using molecular dynamics simulations. By performing a long sub-Tg annealing, we developed a glass model closer to the experiments than the models prepared by continuous cooling. Using the cluster alignment method, we found that “3661” cluster is the dominating short-range order in the glass samples. The connection and arrangement of “3661” clusters, which define the medium-range order in the system, are enhanced significantly in the sub-Tg annealed sample as compared with the fast cooled glass samples. Unlike some strong binary glass formers such as Cu64.5Zr35.5, the clusters representing the short-range order do not form an interconnected interpenetrating network in Al90Sm10, which has only marginal glass formability.
- Published
- 2016
12. Cluster expansion modeling and Monte Carlo simulation of alnico 5–7 permanent magnets
- Author
-
Xin Zhao, Cai-Zhuang Wang, Kai-Ming Ho, and Manh Cuong Nguyen
- Subjects
Materials science ,Magnetic moment ,Condensed matter physics ,Ferromagnetism ,Magnetism ,Magnet ,Monte Carlo method ,engineering ,General Physics and Astronomy ,Alnico ,engineering.material ,Series expansion ,Cluster expansion - Abstract
The concerns about the supply and resource of rare earth (RE) metals have generated a lot of interests in searching for high performance RE-free permanent magnets. Alnico alloys are traditional non-RE permanent magnets and have received much attention recently due their good performance at high temperature. In this paper, we develop an accurate and efficient cluster expansion energy model for alnico 5–7. Monte Carlo simulations using the cluster expansion method are performed to investigate the structure of alnico 5–7 at atomistic and nano scales. The alnico 5–7 master alloy is found to decompose into FeCo-rich and NiAl-rich phases at low temperature. The boundary between these two phases is quite sharp (∼2 nm) for a wide range of temperature. The compositions of the main constituents in these two phases become higher when the temperature gets lower. Both FeCo-rich and NiAl-rich phases are in B2 ordering with Fe and Al on α-site and Ni and Co on β-site. The degree of order of the NiAl-rich phase is much higher than that of the FeCo-rich phase. A small magnetic moment is also observed in NiAl-rich phase but the moment reduces as the temperature is lowered, implying that the magnetic properties of alnico 5–7 could be improved by lowering annealing temperature to diminish the magnetism in NiAl-rich phase. The results from our Monte Carlo simulations are consistent with available experimental results.
- Published
- 2015
13. Structure of Cu64.5Zr35.5 metallic glass by reverse Monte Carlo simulations
- Author
-
Cai-Zhuang Wang, Kai-Ming Ho, Zejun Ding, Xikui W. Fang, and Li Huang
- Subjects
Molecular dynamics ,Materials science ,Amorphous metal ,Pair correlation ,Monte Carlo method ,Physics::Atomic and Molecular Clusters ,Short range order ,Structure (category theory) ,General Physics and Astronomy ,Reverse Monte Carlo ,Statistical physics ,Structured model ,Nuclear Experiment - Abstract
Reverse Monte Carlo simulations (RMC) have been widely used to generate three dimensional (3D) atomistic models for glass systems. To examine the reliability of the method for metallic glass, we use RMC to predict the atomic configurations of a “known” structure from molecular dynamics (MD) simulations, and then compare the structure obtained from the RMC with the target structure from MD. We show that when the structure factors and partial pair correlation functions from the MD simulations are used as inputs for RMC simulations, the 3D atomistic structure of the glass obtained from the RMC gives the short- and medium-range order in good agreement with those from the target structure by the MD simulation. These results suggest that 3D atomistic structure model of the metallic glass alloys can be reasonably well reproduced by RMC method with a proper choice of input constraints.
- Published
- 2014
14. Influence of oriented topological defects on the mechanical properties of carbon nanotube heterojunctions
- Author
-
Wen-Jay Lee, An-Cheng Yang, Jee-Gong Chang, Wan-Sheng Su, Kai-Ming Ho, Yeng-Tseng Wang, and Cai-Zhuang Wang
- Subjects
Molecular dynamics ,Materials science ,Buckling ,law ,Ultimate tensile strength ,General Physics and Astronomy ,Heterojunction ,Carbon nanotube ,Deformation (engineering) ,Composite material ,Crystallographic defect ,law.invention ,Topological defect - Abstract
The mechanical properties of finite-length (5,0)/(8,0) single-walled carbon nanotube (SWCNT) heterojunctions with manipulated topological defects are investigated using molecular dynamics simulation calculations. The results show that the mechanical properties and deformation behavior of SWCNT heterojunctions are mainly affected not only by the diameter of the thinner segment of the SWCNT heterojunction but also by the orientation of the heptagon-heptagon (7-7) pair in the junction region. Moreover, the orientation of the 7-7 pair strongly affects those properties in the compression loading than those in tensile loading. Finally, it is found that the location of buckling deformation in the heterojunctions is dependent on the orientation of the 7-7 pair in the compression.
- Published
- 2013
15. Atomic structure and magnetic properties of Fe1–xCox alloys
- Author
-
Min Ji, Cai-Zhuang Wang, B. N. Harmon, Manh Cuong Nguyen, Xin Zhao, and Kai-Ming Ho
- Subjects
Condensed matter physics ,Magnetic moment ,Chemistry ,Degenerate energy levels ,Alloy ,General Physics and Astronomy ,Crystal structure ,engineering.material ,k-nearest neighbors algorithm ,Condensed Matter::Materials Science ,Ab initio quantum chemistry methods ,Atom ,engineering ,Atomic physics ,Stoichiometry - Abstract
Using genetic algorithm with first-principle calculations, we searched for low-energy crystal structures of Fe1−xCox alloys. We found that Fe1−xCox alloys are highly configurationally degenerate with many additional off-stoichiometric stable structures to the well-known B2 structure. The average magnetic moment of Fe atom increases with concentration of Co in the alloy, while that of Co atom is almost constant, which are consistent with experiments and earlier studies. The magnetic moment of Fe atom is strongly dependent on the number of Co nearest neighbor and it increases with this number.
- Published
- 2012
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.