Ab Initio DFT Study of Ideal Strength of Crystal and Surfaces in Covalent Systems

2008 ◽  
Vol 1086 ◽  
Author(s):  
Yoshitaka Umeno
Keyword(s):  
Tensile Strength ◽  
Ab Initio ◽  
Normal Stress ◽  
Density Functional ◽  
Level Structure ◽  
High Strength ◽  
Nucleation Site ◽  
Dislocation Nucleation ◽  
Ideal Strength ◽  
The Ideal

AbstractAb initio density functional theory (DFT) calculations were performed to examine various factors which may influence the ideal strength, namely multiaxial loading condition and structure with low symmetry. First, the effect of normal stress on the ideal shear strength (ISS) in covalent crystals, Si, C, Ge and SiC, was evaluated. It was found that the response of ISS to normal stress differs depending on the material, while in metals the trend is unchanged. Obtained ISS as a function of normal stress is useful to understand criteria of dislocation nucleation in a pristine crystal because local lattices at the nucleation site undergo superimposed stress components in experiment. Secondly the ideal tensile strength of silicon surface was evaluated to examine how atomistic-level structure affects the mechanical property. The theoretical tensile strength of Si nanofilms with (100) surface, which is flat with dimer-row structures, shows only 20-30% reduction even though the thickness is down to 1 nm, meaning that the flat surface possesses high strength.

An ab initio study of the ideal tensile and shear strength of single-crystal β–Si3N4

2003 ◽  
Vol 18 (5) ◽  
pp. 1168-1172 ◽  
Author(s):  
Shigenobu Ogata ◽  
Naoto Hirosaki ◽  
Cenk Kocer ◽  
Yoji Shibutani
Keyword(s):  
Shear Strength ◽  
Single Crystal ◽  
Ab Initio ◽  
Density Functional ◽  
Strain Curve ◽  
High Strength ◽  
Indentation Hardness ◽  
Ideal Strength ◽  
Vickers Indentation ◽  
The Ideal

In this study, the ideal tensile and shear strength of single-crystal β–Si3N4 was calculated using an ab initio density functional technique. The stress-strain curve of the silicon nitride polymorph was calculated from simulations of uniaxial strain deformation. In particular, the ideal strength calculated for an applied ∈11 tensile strain was estimated to be approximately 57 GPa. Recently, a good correlation was reported between the shear modulus of high-strength materials and the experimentally determined Vickers indentation hardness value. Using the reported correlation an estimate was made of the Vickers indentation hardness of single-crystal β–Si3N4: approximately 20.4 GPa.

Ab-Initio Study of Mechanical Properties of Transition-Metal Aluminides: A Case Study for Al3(V,Ti)

2005 ◽  
Vol 482 ◽  
pp. 139-142
Author(s):  
M. Jahnátek ◽  
M. Krajčí ◽  
J. Hafner
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Tensile Deformation ◽  
Uniaxial Tensile ◽  
Ideal Strength ◽  
Maximal Stress ◽  
Metal Aluminides ◽  
Interatomic Bonding ◽  
The Ideal

On the basis of ab-initio density-functional calculations we have analyzed the character of interatomic bonding in the intermetallic compounds Al3(V,Ti) with the D022 and L12 structures. In all structures we found an enhanced charge density along the Al-(V,Ti) bonds, a characteristic feature of covalent bonding. The bond strength is quantitatively examined by tensile deformations. The ideal strength of Al3V and Al3Ti under uniaxial tensile deformation was found to be significantly higher than that of both fcc Al and bcc V. We investigated also the changes of the interatomic bonding in Al3V during tensile deformations. We found that the covalent interplanar Al- V bonds disappear before reaching the maximal stress. The weakening of the bonding between the atomic planes during the deformation is accompanied by a strengthening of in-plane bonding and an enhanced covalent character of the intraplanar bonds. Interplanar bonding becomes more metallic under tensile deformation.

Performance Analysis of Magnetorheological Rubber Reinforcing Cord Fabric

2015 ◽  
Vol 744-746 ◽  
pp. 1566-1569
Author(s):  
Xian Zhong Chen
Keyword(s):  
Tensile Strength ◽  
Shear Modulus ◽  
Magnetic Particles ◽  
High Strength ◽  
Zero Field ◽  
Rubber Material ◽  
Cord Fabric ◽  
Ideal Framework ◽  
Nylon Cloth ◽  
The Ideal

Magnetorheological rubber material is a kind of composite material of magneto elastic coupling with multi functions, which is composed of magnetic particles and the mixed rubber films with the magnetic properties of the material, but because of its mechanical properties has limited practical use, and nylon cloth which has the advantages of high strength, dimensional stability, can be the ideal framework of magnetorheological rubber. The results show that for the magnetorheological rubber made from the NR/SBR blend, the tensile strength of the magnetorheological rubber with the cord fabric can greatly improve, the tensile strength can reach 17.8MPa, but also can improve the shear modulus of magnetorheological rubber and zero field storage shear modulus.

scholarly journals An independent derivation and verification of the voids nucleation failure mechanism: significance for materials failure

2019 ◽  
Vol 475 (2222) ◽  
pp. 20180755 ◽  
Author(s):  
Richard Christensen ◽  
Zhi Li ◽  
Huajian Gao
Keyword(s):  
Stress State ◽  
Failure Mechanism ◽  
Density Functional ◽  
Failure Modes ◽  
Shear Bands ◽  
Failure Criteria ◽  
Atomic Scale ◽  
Ideal Strength ◽  
Failure Theory ◽  
The Ideal

Independent derivations are given for the failure criteria of the purely dilatational stress state involving voids nucleation failure as well as for the purely distortional stress state involving shear bands failure. The results are consistent with those from a recently derived failure theory and they further substantiate the failure theory. The voids nucleation mechanism is compared with the ideal theoretical strength of isotropic materials as derived by density functional theory and two other atomic-scale methods. It is found that a cross-over occurs from the voids nucleation failure mechanism to the ideal strength limitation as the tensile to compressive strengths ratio, T / C , increases toward a value of unity. All the results are consistent with the failure modes transition results from the general failure theory.

The mechanical properties of perfect crystals I. The ideal strength

1972 ◽  
Vol 330 (1582) ◽  
pp. 291-308 ◽  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Shear Strength ◽  
Sodium Chloride ◽  
Room Temperature ◽  
Cleavage Plane ◽  
Ideal Strength ◽  
Lennard Jones ◽  
Computer Calculations ◽  
The Ideal

In this paper we present computer calculations of the ideal strength of crystals of sodium chloride and argon, for a variety of modes of homogeneous deformation. As models of the interatomic binding we employ the simple, two-body, central-force Born-Mayer and Lennard-Jones potentials respectively. The calculations for argon are appropriate to absolute zero, those for sodium chloride to room temperature. The results indicate a very marked anisotropy of the ideal tensile strength for sodium chloride, with a pronounced minimum at <100>, which is consistent with the observed cleavage on this plane. The ideal tensile strength of argon is shown to be much less dependent on orientation, which accords with the lack of any obvious cleavage plane in this material. We also make some estimates of the ideal shear strength, and find this to be a minimum for {111} <112> shear for both argon and sodium chloride.

scholarly journals Ab initio Structure Prediction Methods for Battery Materials : A review of recent computational efforts to predict the atomic level structure and bonding in materials for rechargeable batteries

2020 ◽  
Vol 64 (2) ◽  
pp. 103-118 ◽  
Author(s):  
Angela F. Harper ◽  
Matthew L. Evans ◽  
James P. Darby ◽  
Bora Karasulu ◽  
Can P. Koçer ◽  
...  
Keyword(s):  
Ab Initio ◽  
Structure Prediction ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Level Structure ◽  
Lithium Ion ◽  
Rechargeable Batteries ◽  
Random Structure ◽  
Voltage Profile ◽  
Battery Materials

Portable electronic devices, electric vehicles and stationary energy storage applications, which encourage carbon-neutral energy alternatives, are driving demand for batteries that have concurrently higher energy densities, faster charging rates, safer operation and lower prices. These demands can no longer be met by incrementally improving existing technologies but require the discovery of new materials with exceptional properties. Experimental materials discovery is both expensive and time consuming: before the efficacy of a new battery material can be assessed, its synthesis and stability must be well-understood. Computational materials modelling can expedite this process by predicting novel materials, both in stand-alone theoretical calculations and in tandem with experiments. In this review, we describe a materials discovery framework based on density functional theory (DFT) to predict the properties of electrode and solid-electrolyte materials and validate these predictions experimentally. First, we discuss crystal structure prediction using the Ab initio random structure searching (AIRSS) method. Next, we describe how DFT results allow us to predict which phases form during electrode cycling, as well as the electrode voltage profile and maximum theoretical capacity. We go on to explain how DFT can be used to simulate experimentally measurable properties such as nuclear magnetic resonance (NMR) spectra and ionic conductivities. We illustrate the described workflow with multiple experimentally validated examples: materials for lithium-ion and sodium-ion anodes and lithium-ion solid electrolytes. These examples highlight the power of combining computation with experiment to advance battery materials research.

The Effect of Impurities on the Ideal Tensile Strength of Covalent Crystals - Ab-Initio Quantum Molecular Dynamics Calculations

1993 ◽  
Vol 327 ◽  
Author(s):  
Y.M. Huang ◽  
J.C.H. Spence ◽  
Otto F. Sankey
Keyword(s):  
Tensile Strength ◽  
Local Density ◽  
Impurity Effect ◽  
Quantum Molecular Dynamics ◽  
Crystalline Solids ◽  
Ideal Strength ◽  
Molecular Dynamics Calculations ◽  
Effect Of Impurities ◽  
Structure Calculations ◽  
The Ideal

AbstractUsing first-principles electronic structure calculations in the local density approximation combined with lattice dynamics, we investigate the effect of III/V impurities on the ideal strength of covalent solids (C, Si, and Ge). Our results show that undoped crystalline solids are stronger in tension along [111] than n-type crystalline solids. P doping has a negligible effect on ideal tensile strength, while n-type doping causes a small reduction in strength of about 6%. The n-type impurity effect is due to the negative (repulsive) contribution from the bottom state of the distorted conduction band to the ideal strength of the solid.

Ideal Strength of Nano-Components

2005 ◽  
Vol 482 ◽  
pp. 25-32 ◽  
Author(s):  
Takayuki Kitamura ◽  
Yoshitaka Umeno ◽  
Akihiro Kushima
Keyword(s):  
High Strength ◽  
Perfect Crystal ◽  
The Other ◽  
Ideal Strength ◽  
Structured Materials ◽  
Recent Developments ◽  
Definition Of ◽  
Nano Wires ◽  
External Loads ◽  
The Ideal

The ideal (theoretical) strength was originally defined as the stress or strain at which perfect crystal lattice became mechanically unstable with respect to arbitrary homogeneous infinitesimal deformation. This has been intensely investigated because the ultimate strength without defects is a fundamental mechanical characteristic of materials. In the analyses, the instability criteria have been studied on the basis of elastic constants. Recent developments in computational technology make it possible to analyze the ideal strength on the basis of quantum mechanics. On the other hand, it is well known that the mechanical strength of components is dependent not only on (1) material (atom species), but also on (2) loading condition and (3) structure. Because most studies on the strength in terms of atomic mechanics have focused on the factor (1) (materials), analysis has mainly been conducted on simple crystal consisting of perfect lattices (e.g. fcc and bcc) under simple loading conditions (e.g. tension), though some have explored the properties of bulk materials with defects (e.g. vacancy and grain boundary). Small atomic components (nano-structured components) such as nano-films, nano-wires (tubes) and nano-dots (clusters) possess their own beautiful, defect-free structures, namely ideal structure. Thus, they show characteristic high strength. Moreover, utilizing the structure at the nanometer or micron level is a key technology in the development of electronic devices and elements of micro (nano) electro-mechanical systems (MEMS/NEMS). Therefore, it is important to understand the mechanical properties not only for the sake of scientific interest, but also for engineering usefulness such as design of fabrication/assembly processes and reliability in service. In the other words, the effects of structure (factor (3); e.g. film/wire/dot) have to be understood as the basic properties of atomic components. Thus, the definition of ideal strength should be expanded to include the strength at instability of components with ideal structures under various external loads (factor (2)), which provides fundamental knowledge of nano-structured materials. In this paper, we review works on the strength of ideal nano-structured components in terms of factor (3), mainly under tension.

A comparative ab initio study of the ‘ideal’ strength of single crystal α- and β-Si3N4

2004 ◽  
Vol 52 (1) ◽  
pp. 233-238 ◽  
Author(s):  
Shigenobu Ogata ◽  
Naoto Hirosaki ◽  
Cenk Kocer ◽  
Yoji Shibutani
Keyword(s):  
Single Crystal ◽  
Ab Initio ◽  
Ideal Strength ◽  
Ab Initio Study ◽  
The Ideal

scholarly journals Calculating Study on Properties of Al (111)/6H-SiC (0001) Interfaces

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1197
Author(s):  
Changqing Wang ◽  
Weiguang Chen ◽  
Yu Jia ◽  
Jingpei Xie
Keyword(s):  
Tensile Strength ◽  
Density Functional ◽  
Adhesion Force ◽  
Adhesion Energy ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Gross Energy ◽  
The Difference ◽  
The Comparative Study ◽  
The Ideal

The research elaborates on the mechanical properties at the Al (111)/6H-SiC (0001) interface based on the density functional theory. Because of the difference in atom category at the interface of 6H-SiC (0001), it takes the C-terminated interface and Si-terminated interface into account. As indicated by the gross energy computing results at the two interfaces, the C-terminated Al (111)/6H-SiC (0001) interface demonstrates a greater adhesion force than the Si-terminated counterpart. Throughout detailed analysis on the bonding mechanism, surface hybridization and charge transfer at the Al (111)/6H-SiC (0001) reaction interface, the research reveals its strong covalent characteristics. According to the comparative study on the ideal tensile strength and general stacking fault energy at varying cleavage surfaces, a conclusion can be fitly reached that the fracture at the Al (111)/6H-SiC (0001) interface is easily seen in Al-Al bonds in the Al matrix instead of C(Si)-Al bonds at the interface. Despite the greater adhesion energy of the C-Al bond than the Si-Al bond, Al-Al bonds close to the C-terminated Al (111)/6H-SiC (0001) interface easily fracture due to the low ideal tensile strength.

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