Site preferences and effects of X (X = Mn, Fe, Co, Cu) on the properties of NiAl: A first-principles study

The site preference of X (X = Mn, Fe, Co, Cu) in NiAl and its effects on structural, electronic and elastic properties were investigated by performing first-principles calculations using density functional theory (DFT). Formation enthalpy calculations show that adding X increases the formation enthalpy of NiAl, indicating that X addition reduces the stability of system. The site preference was investigated by calculating the transfer energy of NiAl alloys with X. The results further exhibit that Mn, Fe and Cu show no site preference, but Co tends to occupy Ni site. By analyzing electronic density of states, Mulliken population, overlap population and valence charge density, the electronic property and bond characters were discussed. The elastic property calculation shows that only substitution of Ni by Cu increased the plasticity of alloy, while in the other cases the plasticity was decreased.

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Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2021-2019 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Nilanjan Roy ◽

Sucharita Giri ◽

Harshit ◽

Partha P. Jana

Keyword(s):

Total Energy ◽

First Principles ◽

Density Functional ◽

Structure Type ◽

Site Preference ◽

X Ray Diffraction ◽

Atomic Ordering ◽

Functional Theory ◽

The Stability ◽

Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

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Effects of Doped Elements (Si, Cr, W and Nb) on the Stability, Mechanical Properties and Electronic Structures of MoAlB Phase by the First-Principles Calculation

Materials ◽

10.3390/ma13194221 ◽

2020 ◽

Vol 13 (19) ◽

pp. 4221

Author(s):

Yongxin Jian ◽

Zhifu Huang ◽

Yu Wang ◽

Jiandong Xing

Keyword(s):

Mechanical Properties ◽

Chemical Bonding ◽

First Principles ◽

Electronic Structures ◽

Density Functional ◽

Formation Enthalpy ◽

First Principles Calculation ◽

Elemental Doping ◽

The Stability ◽

W Doping

First-principles calculations based on density functional theory (DFT) have been performed to explore the effects of Si, Cr, W, and Nb elements on the stability, mechanical properties, and electronic structures of MoAlB ternary boride. The five crystals, with the formulas of Mo4Al4B4, Mo4Al3SiB4, Mo3CrAl4B4, Mo3WAl4B4, and Mo3NbAl4B4, have been respectively established. All the calculated crystals are thermodynamically stable, according to the negative cohesive energy and formation enthalpy. By the calculation of elastic constants, the mechanical moduli and ductility evolutions of MoAlB with elemental doping can be further estimated, with the aid of B/G and Poisson’s ratios. Si and W doping cannot only enhance the Young’s modulus of MoAlB, but also improve the ductility to some degree. Simultaneously, the elastic moduli of MoAlB are supposed to become more isotropic after Si and W addition. However, Cr and Nb doping plays a negative role in ameliorating the mechanical properties. Through the analysis of electronic structures and chemical bonding, the evolutions of chemical bondings can be disclosed with the addition of dopant. The enhancement of B-B, Al/Si-B, and Al/Si-Mo bondings takes place after Si substitution, and W addition apparently intensifies the bonding with B and Al. In this case, the strengthening of chemical bonding after Si and W doping exactly accounts for the improvement of mechanical properties of MoAlB. Additionally, Si doping can also improve the Debye temperature and melting point of the MoAlB crystal. Overall, Si element is predicted to be the optimized dopant to ameliorate the mechanical properties of MoAlB.

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First-Principles Study on Hydrogen Desorption Properties of Li4BN3H10 Doped by Chlorine Anion

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.574.363 ◽

2014 ◽

Vol 574 ◽

pp. 363-367

Author(s):

Cui Cui Du ◽

Tong Shuo Zhang ◽

Tian Fu Gao ◽

Ren Zhong Huang

Keyword(s):

First Principles ◽

Density Functional ◽

Formation Enthalpy ◽

Hydrogen Desorption ◽

Main Peak ◽

Functional Theory ◽

Hydrogen Storage Properties ◽

Chlorine Anion ◽

The Stability ◽

Storage Properties

The hydrogen storage properties of Li4BN3H10doped by Cl anion are investigated by using first-principles method based on density functional theory. According to the calculated results of formation enthalpy and substitution enthalpy, Cl-doping may result in the substitution of H by Cl-in the hydride lattice and accordingly, a favorable thermodynamics modification. The electronic structure analysis indicates that the main peak of H-1s moves close to Fermi level when substituting H-by Cl-. The stability of hydrogen in the doped hydride is lowered compared with that in the hydride without doping, which improves the hydrogen desorption properties of the hydride.

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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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The stability and electronic and photocatalytic properties of the ZnWO4 (010) surface determined from first-principles and thermodynamic calculations

RSC Advances ◽

10.1039/d1ra03218f ◽

2021 ◽

Vol 11 (38) ◽

pp. 23477-23490

Author(s):

Yonggang Wu ◽

Jihua Zhang ◽

Bingwei Long ◽

Hong Zhang

Keyword(s):

Phase Diagram ◽

Density Functional Theory ◽

First Principles ◽

Density Functional ◽

Thermodynamic Calculations ◽

Photocatalytic Properties ◽

Thermodynamic Approach ◽

Functional Theory ◽

Stability Phase Diagram ◽

The Stability

The ZnWO4 (010) surface termination stability is studied using a density functional theory-based thermodynamic approach. The stability phase diagram shows that O-Zn, DL-W, and DL-Zn terminations of ZnWO4 (010) can be stabilized.

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Computational Studies of Magnesium and Strontium Substitution in Hydroxyapatite

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.529-530.123 ◽

2012 ◽

Vol 529-530 ◽

pp. 123-128 ◽

Cited By ~ 1

Author(s):

Flora E. Imrie ◽

Marta Corno ◽

Piero Ugliengo ◽

Iain R. Gibson

Keyword(s):

Density Functional ◽

Structural Changes ◽

Harmonic Approximation ◽

Site Preference ◽

Ionic Radii ◽

Biologically Relevant ◽

Site Preferences ◽

Mechanical Approach ◽

Quantum Mechanical Approach ◽

Mg Substitution

The properties of hydroxyapatite can be improved by substitution of biologically relevant ions, such as magnesium (Mg) and strontium (Sr), into its structure. Previous work in the literature has not reached agreement as to site preferences in these substitutions, and there are suggestions that these may change with differing levels of substitution. The current work adopted a quantum mechanical approach based on density functional theory using the CRYSTAL09 code to investigate the structural changes relating to, and site preferences of, magnesium and strontium substitution (to 10 mol%) in hydroxyapatites and also to predict the corresponding vibrational spectra in the harmonic approximation. The structures underwent full geometrical optimisation within the P63 space group, indicating an energetic site preference for the Ca (2) site in the case of Mg substitution, and the Ca (1) site in the case of Sr. Shrinkage of the unit cell was observed in the case of Mg substitution, and expansion in the case of Sr substitution, in agreement with the corresponding ionic radii. Thermodynamic properties of the structures obtained from the harmonic vibrational frequency calculations confirmed that the structures were minima on the potential energy surface. Isotopic substitutions indicated that the main contribution of Sr and Mg to vibrational modes is at frequencies < 400 cm-1.

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The tuning effect of the electric field on the physical properties of some typical wurtzite semiconductors

Modern Physics Letters B ◽

10.1142/s0217984917503109 ◽

2017 ◽

Vol 31 (33) ◽

pp. 1750310 ◽

Cited By ~ 1

Author(s):

Jia-Ning Li ◽

San-Lue Hu ◽

Hao-Yu Dong ◽

Xiao-Ying Xu ◽

Jia-Fu Wang ◽

...

Keyword(s):

Electric Field ◽

Physical Properties ◽

First Principles ◽

Electronic Structures ◽

Density Functional ◽

Great Influence ◽

Semiconductor Materials ◽

Functional Theory ◽

The Stability ◽

Wurtzite Semiconductors

Under the tuning of an external electric field, the variation of the geometric structures and the band gaps of the wurtzite semiconductors ZnS, ZnO, BeO, AlN, SiC and GaN have been investigated by the first-principles method based on density functional theory. The stability, density of states, band structures and the charge distribution have been analyzed under the electric field along (001) and (00[Formula: see text]) directions. Furthermore, the corresponding results have been compared without the electric field. According to our calculation, we find that the magnitude and the direction of the electric field have a great influence on the electronic structures of the wurtzite materials we mentioned above, which induce a phase transition from semiconductor to metal under a certain electric field. Therefore, we can regulate their physical properties of this type of semiconductor materials by tuning the magnitude and the direction of the electric field.

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First-Principles Calculation of Conductivity of Ce-C Codoped SnO2 Contacts

Advances in Condensed Matter Physics ◽

10.1155/2021/4346979 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Can Ding ◽

Zhenjiang Gao ◽

Xing Hu ◽

Zhao Yuan

Keyword(s):

Charge Density ◽

Lattice Constant ◽

First Principles ◽

Density Functional ◽

Energy Levels ◽

Circuit Breaker ◽

Enthalpy Change ◽

First Principles Calculation ◽

Contact Material ◽

Electronic Density

The contact is the core element of the vacuum interrupter of the mechanical DC circuit breaker. The electrical conductivity and welding resistance of the material directly affect its stability and reliability. AgSnO2 contact material has low resistivity, welding resistance, and so on. This material occupies an important position of the circuit breaker contact material. This research is based on the first-principles analysis method of density functional theory. The article calculated the lattice constant, enthalpy change, energy band, electronic density of state, charge density distribution, population, and conductivity of Ce, C single-doped, and Ce-C codoped SnO2 systems. The results show that Ce, C single doping, and Ce-C codoping all increase the cell volume and lattice constant. When the elements are codoped, the enthalpy change is the largest, and the thermal stability is the best. It has the smallest bandgap, the most impurity energy levels, and the least energy required for electronic transitions. The 4f orbital electrons of the Ce atom and the 2p orbital electrons of C are the sources of impurity energy near the Fermi level. When the elements are codoped, more impurity energy levels are generated at the bottom of the conduction band and the top of the valence band. Its bandgap is reduced so conductivity is improved. From the charge density and population analysis, the number of free electrons of Ce atoms and C atoms is redistributed after codoping. It forms a Ce-C covalent bond to further increase the degree of commonality of electrons and enhance the metallicity. The conductivity analysis shows that both single-doped and codoped conductivity have been improved. When the elements are codoped, the conductivity is the largest, and the conductivity is the best.

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First-Principles Study of Ag3Sn, AgZn3 and Ag5Zn8 Intermetallic Compounds

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.871.254 ◽

2021 ◽

Vol 871 ◽

pp. 254-263

Author(s):

Zhan Cheng ◽

Guan Xing Zhang ◽

Wei Min Long ◽

Svitlana Maksymova ◽

Jian Xiu Liu

Keyword(s):

First Principles ◽

Density Functional ◽

Elastic Anisotropy ◽

Constant Density ◽

Mulliken Population ◽

Covalent Bonds ◽

Functional Theory ◽

The Density Functional Theory ◽

Anisotropy Index ◽

Ionic Bonds

The first-principles calculations by CASTEP program based on the density functional theory is applied to calculate the cohesive energy, enthalpy of formation, elastic constant, density of states and Mulliken population of Ag3Sn、AgZn3 and Ag5Zn8. Furthermore, the elastic properties, bonding characteristics, and intrinsic connections of different phases are investigated. The results show that Ag3Sn、AgZn3 and Ag5Zn8 have stability structural, plasticity characteristics and different degrees of elastic anisotropy; Ag3Sn is the most stable structural, has the strongest alloying ability and the best plasticity. AgZn3 is the most unstable structure, has the worst plasticity; The strength of Ag5Zn8 is strongest, AgZn3 has the weakest strength, the largest shear resistance, and the highest hardness. Ag5Zn8 has the maximum Anisotropy index and Ag3Sn has the minimum Anisotropy index. Ag3Sn、AgZn3 and Ag5Zn8 are all have covalent bonds and ionic bonds, the ionic bonds decrease in the order Ag3Sn>Ag5Zn8>AgZn3 and covalent bonds decreases in the order Ag5Zn8>Ag3Sn>AgZn3.

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

MRS Advances ◽

10.1557/adv.2019.331 ◽

2019 ◽

Vol 4 (44-45) ◽

pp. 2419-2429 ◽

Cited By ~ 1

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.

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