Bulk and (001) Surface Properties of TiAl3 Compound

2011 ◽  
Vol 299-300 ◽  
pp. 417-421
Author(s):  
Li Wang ◽  
Jian Hong Gong ◽  
Jun Gao
Keyword(s):  
Surface Energy ◽  
Structural Relaxation ◽  
Density Functional ◽  
Dominant Role ◽  
Lower Surface ◽  
Heat Of Formation ◽  
Lattice Constants ◽  
Structural And Electronic Properties ◽  
The Stability ◽  
Lower Surface Energy

The structural and electronic properties of bulk and (001) surface of TiAl3 have been examined by the first-principles total-energy pseudopotential method based on density functional theory. The lattice constants and heat of formation of bulk TiAl3 we obtained are in good agreement with the experimental and other theoretical values. The calculated bulk properties indicates that bonding nature in TiAl3 is a combination of metallic and ionic, in which the metallic bonding become the predominate one. the strongest hybridization exist in the DO22 structure, the Al-3p and Ti-3d bonding of TiAl3 play the dominant role in hybridization. The structural relaxation and surface energy for (001) slab have been simulated to make sure the stability of slabs with different atomic layers. Compared to TiB2 (0001) slab, TiAl3 surfaces shows smaller structural relaxation and lower surface energy, furthermore, the charge redistribution of (001) slab shows almost the same characteristics as bulk TiAl3, which confirms structural stability of TiAl3 with (001) slab. This present work makes a beneficial attempt at exploring TiAl3 surface as an ab initio method for studying possible nucleation mechanism of Aluminum on it.

Molecular Dynamics Studies of Surface Nucleation and Crystal Growth of Si on SiO2 Substrates

2005 ◽  
Vol 899 ◽  
Author(s):  
Byoung-Min Lee ◽  
Hong Koo Baik ◽  
Takahide Kuranaga ◽  
Shinji Munetoh ◽  
Teruaki Motooka
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Crystal Growth ◽  
Surface Energy ◽  
Md Simulations ◽  
Lower Surface ◽  
Surface Nucleation ◽  
Lower Surface Energy ◽  
Potential Parameters ◽  
Si Thin Film

AbstractMolecular dynamics (MD) simulations of atomistic processes of nucleation and crystal growth of silicon (Si) on SiO2 substrate have been performed using the Tersoff potential based on a combination of Langevin and Newton equations. A new set of potential parameters was used to calculate the interatomic forces of Si and oxygen (O) atoms. It was found that the (111) plane of the Si nuclei formed at the surface was predominantly parallel to the surface of MD cell. The values surface energy for (100), (110), and (111) planes of Si at 77 K were calculated to be 2.27, 1.52, and 1.20 J/m2, respectively. This result suggests that, the nucleation leads to a preferred (111) orientation in the poly-Si thin film at the surface, driven by the lower surface energy.

The effect of Ru on Ti50Pd50 high temperature shape memory alloy: a first-principles study

MRS Advances ◽  
2019 ◽  
Vol 4 (44-45) ◽  
pp. 2419-2429 ◽  
Author(s):  
R. G. Diale ◽  
R. Modiba ◽  
P. E. Ngoepe ◽  
H. R. Chauke
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Lattice Parameter ◽  
Heat Of Formation ◽  
Partial Substitution ◽  
Martensitic Transformation Temperature ◽  
Functional Theory ◽  
Equilibrium Lattice Parameter ◽  
Strengthening Element ◽  
The Stability

ABSTRACTThe stability of the Ti50Pd50-xRux alloy was investigated using first-principles density functional theory within the plane-wave pseudopotential method. Firstly, the Ti50Pd50 gave equilibrium lattice parameter and lowest heats of formation in better agreement with experimental data to within 3%. The heat of formation decreases with an increase in Ru concentration, consistent with the trend of the density of states which is lowered at the Fermi level as Ru content is increased which suggests stability. It was also found that from the calculated elastic constants the structures showed positive shear modulus above 20 at. % Ru, condition of stability. Furthermore, the addition of Ru was found to strengthen the Ti50Pd50-xRux system at higher concentrations. The thermal coefficients of linear expansion for the Ti50Pd31.25Ru18. 75 are higher at low temperature, and that the TiPd-Ru system tends to expand more at low content of 18.75 at. % Ru than at higher content. Partial substitution of Pd with Ru was found more effective as a strengthening element and may enhance the martensitic transformation temperature of the Ti50Pd50 alloy.

scholarly journals Thermodynamics of manganese oxides: Sodium, potassium, and calcium birnessite and cryptomelane

2017 ◽  
Vol 114 (7) ◽  
pp. E1046-E1053 ◽  
Author(s):  
Nancy Birkner ◽  
Alexandra Navrotsky
Keyword(s):  
Surface Energy ◽  
Surface Area ◽  
Oxidation State ◽  
Manganese Oxides ◽  
Lower Surface ◽  
Surface Energies ◽  
Surface Areas ◽  
Bulk Thermodynamics ◽  
Lower Surface Energy

Manganese oxides with layer and tunnel structures occur widely in nature and inspire technological applications. Having variable compositions, these structures often are found as small particles (nanophases). This study explores, using experimental thermochemistry, the role of composition, oxidation state, structure, and surface energy in the their thermodynamic stability. The measured surface energies of cryptomelane, sodium birnessite, potassium birnessite and calcium birnessite are all significantly lower than those of binary manganese oxides (Mn3O4, Mn2O3, and MnO2), consistent with added stabilization of the layer and tunnel structures at the nanoscale. Surface energies generally decrease with decreasing average manganese oxidation state. A stabilizing enthalpy contribution arises from increasing counter-cation content. The formation of cryptomelane from birnessite in contact with aqueous solution is favored by the removal of ions from the layered phase. At large surface area, surface-energy differences make cryptomelane formation thermodynamically less favorable than birnessite formation. In contrast, at small to moderate surface areas, bulk thermodynamics and the energetics of the aqueous phase drive cryptomelane formation from birnessite, perhaps aided by oxidation-state differences. Transformation among birnessite phases of increasing surface area favors compositions with lower surface energy. These quantitative thermodynamic findings explain and support qualitative observations of phase-transformation patterns gathered from natural and synthetic manganese oxides.

scholarly journals Comparing Study of The Stability and spectral properties vibrations for some Tellurium (IV) compounds containing cycloctadienyl group by Quantum Mechanical Calculations

2013 ◽  
Vol 10 (3) ◽  
pp. 1041-1049
Author(s):  
Baghdad Science Journal
Keyword(s):  
Density Functional ◽  
Heat Of Formation ◽  
Basis Set ◽  
Orbital Energy ◽  
Empirical Methods ◽  
Geometrical Structures ◽  
Functional Theory ◽  
Exchange Correlation ◽  
The Stability ◽  
Semi Empirical

Density Functional Theory (DFT) with B3LYP hybrid exchange-correlation functional and 3-21G basis set and semi-empirical methods (PM3) were used to calculate the energies (total energy, binding energy (Eb), molecular orbital energy (EHOMO-ELUMO), heat of formation (?Hf)) and vibrational spectra for some Tellurium (IV) compounds containing cycloctadienyl group which can use as ligands with some transition metals or essential metals of periodic table at optimized geometrical structures.

Can THF hydrogen bond to glycine as strong as water?

2017 ◽  
Vol 95 (6) ◽  
pp. 664-673 ◽  
Author(s):  
Damanjit Kaur ◽  
Geetanjali Chopra ◽  
Rajinder Kaur
Keyword(s):  
Hydrogen Bond ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Dominant Role ◽  
Basis Set ◽  
Hydrogen Bond Donor ◽  
Orbital Theory ◽  
Interaction Terms ◽  
Stability Of Complexes ◽  
The Stability

Hydrogen bond complexation between glycine and THF and between glycine and water involving four lowest-energy glycine conformers have been studied. The complexes have been investigated in the gas phase at the ab initio molecular orbital theory (MP2) with aug-cc-pVDZ basis set and density functional theory (B3LYP) with aug-cc-pVTZ basis set. Bader’s theory of atoms in molecules (AIM), natural bond orbital (NBO), and symmetry adapted perturbation theory (SAPT) analyses are employed to elucidate the interaction characteristics in the complexes. The premise that the hydrogen bond donor ability of the O–H group of the carboxyl group dominates the interaction between glycine and THF and between glycine and water is confirmed. It is found that in comparison with water, THF binds more strongly to glycine. The quantum studies indicate that contribution of N–H···O and C–H···O hydrogen bonds in the complexes, although lower in magnitude to O–H···O interactions, play an important role in the stability of complexes. The blue and red shifts in the stretching frequencies of the hydrogen bond donors X–H (X = O, C, N) have also been related to stabilization energies. Decomposition of the stabilization energy based on the SAPT method clearly indicates the dominant role of the electrostatic interactions in all the complexes under study; however, induction and dispersion interaction terms are relatively higher in glycine–THF complexes.

Stability and Electronic Structures of Mg2Pb (100), (110) and (111) Surfaces

2015 ◽  
Vol 817 ◽  
pp. 690-697
Author(s):  
Yong Hua Duan ◽  
Yong Sun ◽  
Ming Jun Peng
Keyword(s):  
Density Functional Theory ◽  
Surface Energy ◽  
Density Of States ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Dft Method ◽  
Functional Theory ◽  
Charge Density Difference ◽  
The Stability

The stability and electronic properties of Mg2Pb (100), (110) and (111) surfaces were investigated by using the first-principles density functional theory (DFT) method. The calculated results showed that the orders of relaxation and surface energy are |∆d15(111)| < |∆d15(110)| < |∆d15(100)| andEsurf(100) >Esurf(110) >Esurf(111), respectively, indicating that Mg2Pb (111) surface is the most stable among these three low index surfaces. The Density of states (DOS) of Mg2Pb surfaces are mainly dominated by Pb-6, Mg-3s, and 2porbitals in the band ranging from-5 eV to Fermi level. It can be further obtained from results of the DOS and the charge density difference that Mg2Pb (111) surface is more stable than Mg2Pb (100) and (110) surfaces. The Mg2Pb (111) surface is the thermodynamically most favorable over all of the range of.

DFT study of the structural and electronic properties of crystalline 2-benzylidene-1-indanone under different hydrostatic pressures

2017 ◽  
Vol 28 (06) ◽  
pp. 1750072
Author(s):  
Ying Guo ◽  
Yongcun Ding ◽  
Qingqing Liu ◽  
Xiangqiang Zhao
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Pressure Range ◽  
Structural Transformations ◽  
Absorption Properties ◽  
Functional Theory ◽  
Lattice Constants ◽  
Structural And Electronic Properties ◽  
Electronic Character

In this work, we use density functional theory (DFT) calculations to study the structural, electronic and absorption properties of crystalline 2-benzylidene-1-indanone (signed as 2-BI) in the pressure range of 0–300[Formula: see text]GPa. The detailed analysis of the variation tendencies of the lattice constants, bond lengths and bond angles with increasing pressures shows that there occur several transformations in 2-BI under different pressures. In addition, it can be see that the [Formula: see text]- and [Formula: see text]-axis are much stiffer than the [Formula: see text]-axis in the structure of 2-BI, suggesting the crystal is anisotropic. Then, the analysis of the band gap and DOS (PDOS) of 2-BI indicate that its electronic character has changed at 120[Formula: see text]GPa into metal phase, but then transfer into excellent insulator at 230[Formula: see text]GPa. Moreover, the relatively high optical activity with the increasing pressure of 2-BI is seen from the absorption spectra, and three obvious structural transformations are also observed at 60, 120 and 250[Formula: see text]GPa, respectively.

scholarly journals INVESTIGATIONS OF RESISTANCE TO SEIZING OF LASER-TEXTURED ELEMENTS

1970 ◽  
pp. 3-6
Author(s):  
Bogdan Antoszewski
Keyword(s):  
Surface Energy ◽  
Lower Surface ◽  
Texture Effect ◽  
Lower Surface Energy

The paper presents results of experiments concerning the assessment of the texture effect on scuffing resistance. The results showed that texturing  causes an increase in scuffing resistance. In addition, textures showing lower surface energy and having higher volume were found  to form surfaces more resistant to scuffing.

Density Functional Theory Study of Magnesium Surface

2012 ◽  
Vol 554-556 ◽  
pp. 1609-1612
Author(s):  
Shan Qisong Huang ◽  
Xiu Lin Zeng ◽  
Xue Hai Ju ◽  
Si Yu Xu
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Lower Surface ◽  
State Density ◽  
Experimental Result ◽  
Density Functional Theory Study ◽  
Density Of State ◽  
Functional Theory ◽  
Magnesium Surface ◽  
Lower Surface Energy

Density functional theory (DFT) calculations were performed on seven magnesium surfaces of Mg(100), Mg(010), Mg(001), Mg(110), Mg(101), Mg(011) and Mg(111). The electronic state density was analyzed. The stabilities of the seven surfaces were established. The results indicated that the surface energies are in the range of 0.4610 to 1.0940 J/m2, which correspond to the Mg(001) and Mg(101) surfaces respectively. These data agree well with the available experimental result. In addition, it was found that the lower surface energy corresponds to more evenly distributed density of state (DOS), more number of DOS peaks but less height of it.

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