scholarly journals Computational Modeling of Tensile Stress Effects on the Structure and Stability of Prototypical Covalent and Layered Materials

2019 ◽  
Author(s):  
Hocine Chorfi ◽  
Alvaro Lobato ◽  
Fahima Boudjada ◽  
Miguel Ángel Salvadó ◽  
Ruth Franco ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Density Functional ◽  
Stability Limit ◽  
Density Functional Theory Calculations ◽  
Layered Materials ◽  
Stress Conditions ◽  
Ideal Strength ◽  
Critical Strength ◽  
Calculated Stress ◽  
The Stability

Understanding the stability limit of crystalline materials under variable tensile stress conditions is of capital interest for their technological applications. In this study, we present results from first-principles density functional theory calculations that quantitatively account for the response of selected covalent and layered materials to general stress conditions. In particular, we have evaluated the ideal strength along the main crystallographic directions of 3C and 2H polytypes of SiC, hexagonal ABA stacking of graphite and 2H-MoS2. Transverse superimposed stress on the tensile stress was taken into account in order to evaluate how the critical strength is affected by these multi-load conditions. In general, increasing transverse stress from negative to positive values leads to the expected decreasing of the critical strength. Few exceptions found in the compressive stress region correlate with the trends in the density of bonds along the directions with the unexpected behavior. In addition, we propose a modified spinodal equation of state able to accurately describe the calculated stress-strain curves. This analytical function is of general use and can also be applied to experimental data anticipating critical strengths and strains values and providing informattion on the energy stored in tensile stress processes.

scholarly journals Computational Modeling of Tensile Stress Effects on the Structure and Stability of Prototypical Covalent and Layered Materials

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1483 ◽  
Author(s):  
Hocine Chorfi ◽  
Álvaro Lobato ◽  
Fahima Boudjada ◽  
Miguel A. Salvadó ◽  
Ruth Franco ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Density Functional ◽  
Stability Limit ◽  
Density Functional Theory Calculations ◽  
Layered Materials ◽  
Stress Conditions ◽  
Ideal Strength ◽  
Critical Strength ◽  
Calculated Stress ◽  
The Stability

Understanding the stability limit of crystalline materials under variable tensile stress conditions is of capital interest for technological applications. In this study, we present results from first-principles density functional theory calculations that quantitatively account for the response of selected covalent and layered materials to general stress conditions. In particular, we have evaluated the ideal strength along the main crystallographic directions of 3C and 2H polytypes of SiC, hexagonal ABA stacking of graphite and 2H-MoS 2 . Transverse superimposed stress on the tensile stress was taken into account in order to evaluate how the critical strength is affected by these multi-load conditions. In general, increasing transverse stress from negative to positive values leads to the expected decreasing of the critical strength. Few exceptions found in the compressive stress region correlate with the trends in the density of bonds along the directions with the unexpected behavior. In addition, we propose a modified spinodal equation of state able to accurately describe the calculated stress–strain curves. This analytical function is of general use and can also be applied to experimental data anticipating critical strengths and strain values, and for providing information on the energy stored in tensile stress processes.

Targeting complex plutonium oxides by combining crystal chemical reasoning with density-functional theory calculations: the quaternary plutonium oxide Cs2PuSi6O15

2020 ◽  
Vol 56 (66) ◽  
pp. 9501-9504
Author(s):  
Kristen A. Pace ◽  
Vladislav V. Klepov ◽  
Matthew S. Christian ◽  
Gregory Morrison ◽  
Travis K. Deason ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Crystal Growth ◽  
Dft Calculations ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Crystal Chemical ◽  
The Novel ◽  
Functional Theory ◽  
The Stability ◽  
Chemical Reasoning

The stability of the novel Pu(iv) silicate, Cs2PuSi6O15, was predicted from a combination of crystal chemical reasoning and DFT calculations and confirmed by its synthesis via flux crystal growth.

Chemical vapor deposition of layered two-dimensional MoSi2N4 materials

Science ◽  
2020 ◽  
Vol 369 (6504) ◽  
pp. 670-674 ◽  
Author(s):  
Yi-Lun Hong ◽  
Zhibo Liu ◽  
Lei Wang ◽  
Tianya Zhou ◽  
Wei Ma ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Density Functional ◽  
Chemical Vapor ◽  
Large Family ◽  
Density Functional Theory Calculations ◽  
Layered Materials ◽  
Molybdenum Nitride ◽  
Two Dimensional ◽  
Chemical Vapor Deposition Growth

Identifying two-dimensional layered materials in the monolayer limit has led to discoveries of numerous new phenomena and unusual properties. We introduced elemental silicon during chemical vapor deposition growth of nonlayered molybdenum nitride to passivate its surface, which enabled the growth of centimeter-scale monolayer films of MoSi2N4. This monolayer was built up by septuple atomic layers of N-Si-N-Mo-N-Si-N, which can be viewed as a MoN2 layer sandwiched between two Si-N bilayers. This material exhibited semiconducting behavior (bandgap ~1.94 electron volts), high strength (~66 gigapascals), and excellent ambient stability. Density functional theory calculations predict a large family of such monolayer structured two-dimensional layered materials, including semiconductors, metals, and magnetic half-metals.

DFT STUDIES ON THE STABILITY OF THE TRANS AND CIS ISOMERS IN THE SQUARE PLANAR PALLADIUM(II) COMPLEXES Pd(I)(PPh3)(η3-XCHC(Ph)CHR) (X = CMe3, CO2Me, P(O)(OMe)2, AND SO2H; R = H, Me)

2008 ◽  
Vol 07 (04) ◽  
pp. 505-515
Author(s):  
LIQIN XUE ◽  
GUOCHEN JIA ◽  
ZHENYANG LIN
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Relative Stability ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Dft Studies ◽  
Functional Theory ◽  
Square Planar ◽  
The Stability ◽  
Cis Isomer

The relative stability of the trans and cis isomers in the square planar palladium(II) complexes Pd ( I )( PPh 3)(η3- XCHC ( Ph ) CHR ) ( X = H , Me , CMe 3, CO 2 Me , P ( O )( OMe )2, and SO 2 H ; R = H , Me ) was investigated with the aid of the B3LYP density functional theory calculations. We examined how the substituents X, with different electronic properties, of the η3-allyl ligands affect the relative stability of the trans and cis isomers. Through the investigation, we were able to explain the trans/cis relative stability derived from the experimentally measured trans/cis isomer ratios in the palladium(II) complexes.

Exploring halide anion affinities to native cyclodextrins by mass spectrometry and molecular modelling

2017 ◽  
Vol 24 (3) ◽  
pp. 269-278 ◽  
Author(s):  
Chongsheng Xu ◽  
Nan He ◽  
Zhenhua Li ◽  
Yanqiu Chu ◽  
Chuan-Fan Ding
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Binding Constants ◽  
Density Functional Theory Calculations ◽  
Collision Induced Dissociation ◽  
Binding Affinities ◽  
Cyclodextrin Complex ◽  
Halide Anion ◽  
Mass Frame ◽  
The Stability

The binding affinities of cyclodextrins complexation with chlorine (Cl−), bromine (Br−) and iodine (I−), were measured by mass spectrometric titrimetry, and the fitting of the binding constants was based on the concentration measurement of the cyclodextrin equilibrium. The binding constants (lg Ka) for α-, β- or γ-cyclodextrin with Cl− were 3.99, 4.03 and 4.11, respectively. The gas-phase binding affinity of halide anions for native cyclodextrins was probed by collision-induced dissociation. In collision-induced dissociation, the centre-of-mass frame energy results revealed that in the gas phase, for the same type of cyclodextrin, the stability of the complexes decreased in order: Cl > Br > I, and for the same halide anion, the binding stability of the complex with α-, β- or γ-cyclodextrin decreased in the order: γ-cyclodextrin >β-cyclodextrin > α-cyclodextrin. The density functional theory calculations showed that halide anion binding on the primary face had a lower energy than the secondary face and hydrogen bonding was the main driving force for complex formation. The higher stability of the γ-cyclodextrin complex with the Cl anion can be attributed to the higher charge density of the Cl anion and better flexibility of γ-cyclodextrin.

Stability, Electronic Properties, and Structural Isomerism in Small Copper Clusters

2012 ◽  
Vol 1479 ◽  
pp. 15-20
Author(s):  
Juan M. Montejano-Carrizales ◽  
Faustino Aguilera-Granja ◽  
Ricardo A. Guirado-López
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
Three Dimensional ◽  
Density Functional Theory Calculations ◽  
Energy Barriers ◽  
Elastic Band ◽  
Experimental Conditions ◽  
Atomic Displacements ◽  
Structural Isomerism ◽  
The Stability

ABSTRACTWe present extensive pseudopotential density functional theory calculations dedicated to analyze the stability, electronic properties, and structural isomerism in Cu6 clusters. We consider structures of different symmetries and charge states. Our total energy calculations reveal a strong competition between two- and three-dimensional atomic arrays, the later being mostly energetically preferred for the anionic structures. The bond lengths and electronic spectra strongly depend on the local atomic environment, a result that is expected to strongly influence the catalytic activity of our clusters. Using the nudged elastic band method we analyze the interconversion processes between different Cu6 isomers. Complex atomic relaxations are obtained when we study the transition between different cluster structures; however relatively small energy barriers of approximately 0.3 eV accompany the atomic displacements. Interestingly, we obtain that by considering positively charged Cu6+ systems we reduce further the energy barriers opposing the interconversion process. The previous results could imply that, under a range of experimental conditions, it should be possible to observe different Cu6cluster structures in varying proportions.

Density Functional Theory Calculations of Properties of the Grain Boundaries in Aluminum

2011 ◽  
Vol 1297 ◽  
Author(s):  
Marek Muzyk ◽  
Krzysztof J. Kurzydlowski
Keyword(s):  
Density Functional Theory ◽  
Grain Boundaries ◽  
Density Functional ◽  
Quantitative Description ◽  
Aluminum Matrix ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Nano Crystalline ◽  
The Density Functional Theory ◽  
The Stability

ABSTRACTThe Density Functional Theory has been used to analyze an inter-granular segregation of Cu and Mg. The stability of Cu and Mg atoms in the aluminum matrix, intermetallic phases and symmetric twist grain boundaries has been compared. The quantitative description of solubility of Cu and Mg atoms in the nano-crystalline aluminum has been proposed. The calculations have been carried out to investigate the properties of symmetric twist boundaries in aluminum with and without Cu/Mg atoms. The phenomena of are discussed and its effect on the stability of precipitates containing these elements.

scholarly journals Pressure-induced phase transitions in Na2B12H12, structural investigation on a candidate for solid-state electrolyte

2019 ◽  
Vol 75 (3) ◽  
pp. 406-413 ◽  
Author(s):  
Romain Moury ◽  
Zbigniew Łodziana ◽  
Arndt Remhof ◽  
Léo Duchêne ◽  
Elsa Roedern ◽  
...  
Keyword(s):  
High Pressure ◽  
Solid State ◽  
Bulk Modulus ◽  
Density Functional ◽  
Ambient Pressure ◽  
Density Functional Theory Calculations ◽  
Ionic Conductors ◽  
Theoretical Predictions ◽  
Primary Order ◽  
The Stability

closo-Borates, such as Na2B12H12, are an emerging class of ionic conductors that show promising chemical, electrochemical and mechanical properties as electrolytes in all-solid-state batteries. Motivated by theoretical predictions, high-pressure in situ powder X-ray diffraction on Na2B12H12 was performed and two high-pressure phases are discovered. The first phase transition occurs at 0.5 GPa and it is persistent to ambient pressure, whereas the second transition takes place between 5.7 and 8.1 GPa and it is fully reversible. The mechanisms of the transitions by means of group theoretical analysis are unveiled. The primary-order parameters are identified and the stability at ambient pressure of the first polymorph is explained by density functional theory calculations. Finally, the parameters relevant to engineer and build an all-solid-state battery, namely, the bulk modulus and the coefficient of the thermal expansion are reported. The relatively low value of the bulk modulus for the first polymorph (14 GPa) indicates a soft material which allows accommodation of the volume change of the cathode during cycling.

scholarly journals Advanced study of hydrogen storage by substitutional doping of Mn and Ti in Mg2Ni phase

2014 ◽  
Vol 5 ◽  
pp. A24 ◽  
Author(s):  
Omar Elkedim ◽  
Liwu Huang ◽  
David Bassir
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Storage ◽  
First Principles ◽  
Density Functional ◽  
Lattice Site ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Substitutional Doping ◽  
The Stability ◽  
Ti Substitution

The substitutional doping of Mn and Ti in Mg2Ni phase has been investigated by first principles density functional theory calculations. The calculation of enthalpy of formation shows that among the four different lattice sites of Mg(6f), Mg(6i), Ni(3b) and Ni(3d) in Mg2Ni unit cell, the most preferable site of substitution of Mn in Mg2Ni lattice has been confirmed to be Mg(6i) lattice site. The most preferable site of Ti substitution in Mg2Ni lattice is Mg(6i) position and the stability of Ti-doped Mg2Ni decreases with the increase of substitution quantity of Ti for Mg.

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