Prediction of diffusivities in fcc phase of the Al–Cu–Mg system: First-principles calculations coupled with CALPHAD technique

The Bi-M (M = Ti, Cr, V) systems have been critically reviewed and modeled by means of the CALPHAD technique. All the intermetallics (BiTi3, BiTi2, Bi9Ti8, Bi3Ti2 and Bi2Ti) were treated as stoichiometric compounds. The enthalpy of formation at 0 K for BiTi2 was computed via first-principles calculations to assist the thermodynamic modeling. The gas phases for the Bi-Cr and Bi-V systems were treated as ideal gas. A set of self-consistent thermodynamic parameters has been finally obtained for each of these binary systems. Comparisons between the calculated and measured phase diagrams as well as first-principles calculations show that most of experimental data can be satisfactorily reproduced by the present thermodynamic descriptions.

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Compensation between Surface Energy and hcp/fcc Phase Energy of Late Transition Metals from First-Principles Calculations

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.0c02142 ◽

2020 ◽

Vol 124 (20) ◽

pp. 11005-11014

Author(s):

Hao Lin ◽

Jin-Xun Liu ◽

Hongjun Fan ◽

Wei-Xue Li

Keyword(s):

Transition Metals ◽

Surface Energy ◽

First Principles ◽

First Principles Calculations ◽

Late Transition Metals ◽

Late Transition ◽

Fcc Phase

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Effect of Ti Content on the Microstructure and Corrosion Resistance of CoCrFeNiTix High Entropy Alloys Prepared by Laser Cladding

Materials ◽

10.3390/ma13102209 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2209 ◽

Cited By ~ 1

Author(s):

Xinyang Wang ◽

Qian Liu ◽

Yanbin Huang ◽

Lu Xie ◽

Quan Xu ◽

...

Keyword(s):

Corrosion Resistance ◽

Laser Cladding ◽

First Principles ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

First Principles Calculations ◽

High Entropy ◽

Niti Phase ◽

Fcc Phase ◽

Ti Content

In this paper, CoCrFeNiTix high entropy alloy (HEA) coatings were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, and corrosion resistance of the coatings were studied. The mechanism of their corrosion resistance was elucidated experimentally and by first-principles calculations. The results show that CoCrFeNiTi0.1 adopts a face-centered cubic (FCC) phase, CoCrFeNiTi0.3 exhibits an FCC phase and a tetragonal FeCr phase, and CoCrFeNiTi0.5 adopts an FCC phase, a tetragonal FeCr phase, and a rhombohedral NiTi phase. The FCC phase, tetragonal FeCr phase, rhombohedral NiTi phase, and hexagonal CoTi phase are all observed in the CoCrFeNiTi0.7 HEA. The alloys assume the dendritic structure that is typical of HEAs. Ni and Ti are enriched in the interdendritic regions, whereas Cr and Fe are enriched in the dendrites. With increasing Ti content, the hardness of the cladding layers also increases due to the combined effects of lattice distortion and dispersion strengthening. When exposed to a 3.5 wt.% NaCl solution, pitting corrosion is the main form of corrosion on the CoCrFeNiTix HEA surfaces. The corrosion current densities of CoCrFeNiTix HEAs are much lower than those of other HEAs. As the Ti content increases, the corrosion resistance is improved. Through X-ray photoelectron spectroscopy (XPS) and first-principles calculations, the origin of the higher corrosion resistance of the coatings is connected to the presence of a dense passivation film. In summary, the corrosion resistance and mechanical properties of CoCrFeNiTi0.5 alloy are much better than the other three groups, which promotes the development of HEA systems with high value for industrial application.

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Electronic Structure and X-ray Absorption Spectra of Rutile TiO2 Using First-Principles Calculations

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2014.52.12.1025 ◽

2014 ◽

Vol 52 (12) ◽

pp. 1025-1029

Author(s):

Min-Wook Oh ◽

Tae-Gu Kang ◽

Byungki Ryu ◽

Ji Eun Lee ◽

Sung-Jae Joo ◽

...

Keyword(s):

Electronic Structure ◽

Absorption Spectra ◽

First Principles ◽

First Principles Calculations ◽

Rutile Tio2 ◽

X Ray ◽

X Ray Absorption

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To Bend or Not to Bend, the Dilemma of Multiple Bonds

10.26434/chemrxiv.8066747.v1 ◽

2019 ◽

Author(s):

Michele Pizzocchero ◽

Matteo Bonfanti ◽

Rocco Martinazzo

Keyword(s):

First Principles ◽

2D Materials ◽

Main Group ◽

First Principles Calculations ◽

Group 14 ◽

Multiple Bonds ◽

Main Group Elements ◽

Structural Distortions

The manuscript addresses the issue of the structural distortions occurring at multiple bonds between high main group elements, focusing on group 14. These distortions are known as trans-bending in silenes, disilenes and higher group analogues, and buckling in 2D materials likes silicene and germanene. A simple but correlated \sigma + \pi model is developed and validated with first-principles calculations, and used to explain the different behaviour of second- and higher- row elements.

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Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

10.26434/chemrxiv.8052218.v3 ◽

2019 ◽

Author(s):

Henrik Pedersen ◽

Björn Alling ◽

Hans Högberg ◽

Annop Ektarawong

Keyword(s):

Thin Films ◽

Thermodynamic Stability ◽

First Principles ◽

Thermal Equilibrium ◽

Density Functional ◽

Van Der Waals ◽

Chemical Vapor ◽

First Principles Calculations ◽

Functional Theory ◽

The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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