Search

MnPt-based alloys are promising new materials for magnetic recording and spintronic applications due to their interesting magnetic properties. The underlying thermodynamic properties are still unclear, despite numerous efforts to improve ferromagnetic stability through alloying. In this work, the phase stability of B2 and L10 PtMn1-xFex alloys is investigated using a combination of density functional theory (DFT) and Cluster Expansion (CE). CE model accuracy is evaluated against DFT data, where cross-validation scores were found to be reasonable. The CE generated 16 and 27 new structures on B2 and L10 PtMn1-xFex, respectively. The ground state line predicted 6 stable structures with negative formation energies for both B2 and L10 PtMn1-xFex alloys, suggesting thermodynamic stability. Furthermore, the magnetic strength of the ground state structures is evaluated using DFT.

Β2-ordered FeAl and Fe3Al composition amongst other various compounds of transition metals and aluminium compositions have been of significance to researchers for application in industries for steel-IT coating purposes due to their well-adherent protective oxide layer that forms on the surface of such alloys at the metal/gas interface. We employed Cluster expansion (CE) technique to predict meta-stable and stable compositions of Fe1-XPd/IrXAl ternary. A Cluster Expansion phase diagram was predicted, with five stable Fe1-XPdXAl structures and three stable Fe1-XIrXAl structures having the lowest formation energies, respectively. Employed a first-principles approach to predict the mechanical properties, with four and two Pd and Ir ternary doped ductile structures and DMol3 technique to determine temperature dependence dynamical properties, that is, the binding energy of Fe50Al50, FePdAl2 and FeIrAl2 at various temperatures. Our findings showed that doping on FeAl with Pd and Ir significantly enhanced the binding energy that more energy would be required to disassemble the particles of the Ir system into individual parts; the hardness and ductility of the material for high-temperature application component coating for steel-IT superior protection.

Monazite-(La) has received significant attention due to its interesting physical and chemical properties, such as its high fusion temperature and low solubility. It is useful for applications such as lusting, temperature coating, and proton conduction. The density functional theory (DFT) calculations were carried out to investigate the effect of pressure on the structural and thermodynamic properties of Monazite-La from 0 to 60 GPa. Lattice parameters at zero pressure were found to be in good agreement with experimental studies. Furthermore, the thermodynamic properties predicted that the stability of LaPO4 increased with an increase in pressure. The findings provide a deeper understanding of the structural and thermodynamic properties of Monazite-La under pressure.

In the Kroll process, the reduction process results in the production of intermediates such as titanium trichloride (TiCl3) and titanium dichloride (TiCl2). There has been experimental work on developing a continuous reduction process using TiCl3 and TiCl2. However, more investigations still need to be done to understand these mediums and their interactions. In this paper, we will be investigating one TiCl3 polymorph as a potential medium for titanium production. We employ the DL_POLY code to understand the effect of temperature on the Ti7 cluster using a stable β-TiCl3 medium. It was observed from the total energies that the system is stable at 50 – 700 K. The diffusion coefficient results showed that the Ti7 nanocluster diffuses faster than Ti and Cl at 1300 – 2000 K.

This study presents the analysis of the microstructure and Vickers micro-hardness of β-Ti type Ti-15.05Mo alloy obtained by different cooling rates. The alloy was fabricated using an arc-melting furnace, solution treated in a muffle furnace and cooled using different cooling medium such as ice water, furnace cool and air cooling. The X-ray analysis of the as-cast showed β phases peaks only and water quenched samples showed peaks belonging to α″ and β phases. The (β, α) dual phases were detected in the furnace and air-cooled samples, respectively. The Optical Microscope (OM) micrographs of the as-cast Ti-15.05Mo sample showed large equiaxed β grains and sub-structures belonging to orthorhombic martensitic α″ phase. The water quenched sample showed β equiaxed grains, however their grains were much smaller You should leave 8 mm of space above the abstract and 10 mm after the abstract. The heading Abstract should be typed in bold 9-point Arial. The body of the abstract should be typed in normal 9-point Times in a single paragraph, immediately following the heading. The text should be set to 1 line spacing. The abstract should be centred across the page, indented 17 mm from the left and right page margins and justified. It should not normally exceed 200 words.

Bimetallic transition metal nanoclusters have attracted significant attention in recent years due to their wide range of applications such as heterogeneous catalysts, electrochemistry and alloy design. However many studies were reported on pure transition metal nanoclusters and bimetallic of late transition metal nanoclusters. In this study the density functional theory (DFT) with PBEsol exchange correlation functional was employed to investigate the structural and electronic properties of TiN-1Os (N = 2-16) nanoclusters. The calculations showed that osmium impurity mostly prefers to be encapsulated by titanium nanoclusters. The binding energies gradually decrease with the cluster size N. The Os dopant was found to enhance the binding energy of titanium nanoclusters. The relative stability or second order energies showed that Ti6Os and Ti12Os clusters are the most stable. Interestingly, osmium dopant converted the nanocluster with 13 atoms to be the most stable. Furthermore, the dissociation energy or first order energies showed an excellent correlation with the relative stability trend. The HOMO-LUMO revealed the lowest energy gap at Ti12Os (N = 13) which correlates well with the predicted binding energy, relative stability and dissociation energy.

In this study, the ab initio density functional theory (DFT) approach is used to investigate the effect of Holmium (Ho) on the magnetic and mechanical properties of Nd2Fe14B magnets. Neodymium-based permanent magnets (Nd2Fe14B) are the potential permanent magnets to be used in various applications such as wind turbines and electric vehicles. These magnets possess high magnetic field strength and resistance to demagnetization. However, they suffer from low operating temperatures below 585 K. Substitution of Nd with Ho enhances the magnetic strength of the Nd2Fe14B permanent magnet. NdHoFe14B magnets are found to be thermodynamically stable due to negative heats of formation, which is in good agreement with the calculated density of states. Partial substitution of Nd with Ho improves the stability and the magnetic strength of Nd2Fe14B permanent magnets. The findings will provide insight into the future development of permanent magnetic compounds with good magnetic strength.

More recently, the L10 MnPt alloy has received massive attention in data storage applications such as spintronics due to its high ferromagnetic stability and very high Néel temperature. It was found that L10 MnPt alloy showed ferromagnetic behaviour at room temperature. In this study, the effect of introducing antiferromagnetic (Cr) and ferromagnetic (Fe) elements on MnPt alloy is being investigated using density functional theory (DFT). The thermodynamic stability was determined from the heats of formation to check the formability of Pt50Mn50-xMx (M= Cr, Fe; x=6.25, 12.5, 18.75, 25) alloys. These Pt50Mn50-xMx alloys were found to be thermodynamically stable although with lower heats of formation. Overall magnetic moments decrease slightly with an increase in Cr and Fe compositions, only at 6.25 at. % Cr the ferromagnetic state is improved when the c/a ratio is 1.10. The current work revealed that the DFT-based first-principle approach can be used to design new possible compositions for the development of PGM-bearing magnetic materials.

Cesium-chloride (CsCl) based intermetallic alloys that are formed between Ti and Group VIIIB and IB metals (Fe, Ni, Ru, Rh, Pd, Os Ir, Pt and Au) are currently explored for various potential applications as hydrogen storage, shape memory and biomedical materials. These compounds display excellent structural properties such as high strength due to their stable B2 phase at elevated temperatures. However, when some are subjected to unfavourable conditions such as lower temperature they become unstable and undergo a phase transition to low symmetry phases. In this work, we conducted a detailed comparative study using both VASP and CASTEP codes to carry out the first-principles calculations. Phase stability and martensitic phase transition were evaluated from the enthalpies of formation, the density of states as well as the phonon dispersion curves. There was no frequency gap observed on phonons density of states (PHDOS) spectra of the investigated compounds containing noble transition metals due to higher d-orbital electron filling.

Pyrolusite (β-MnO2) was investigated for potential use in energy storage devices due to its promising properties for cathode materials in rechargeable lithium-ion batteries. A combination of evolutionary algorithm search techniques and density functional theory techniques were used to determine the structural stabilities of the β-MnO2 nanoclusters on the energy landscape. However, pyrolusite suffers from some structural defects and impurities that hinder its optimal use. The predicted order of stability for the MnO2 nanoclusters correlates with isostructural TiO2. There is an improvement in the stability and electrical conductivity of the nanoclusters as compared to their β-MnO2 bulk counterparts. The cobalt doped nanoclusters showed a preference toward circular compact bonding patterns. The band-gap energy revealed that the nanoclusters have a metallic characteristic behaviour with narrow band gap energies, indicating their good conductive properties. Cobalt doping was shown to improve the structural properties of the nanoclusters based on the decreased bond lengths and more spherical bond angles. Moreover, it also succeeded in improving the conductivity of the nanoclusters based on the reduced Mulliken and Hirshfeld partial charges. The electronic charge density differences of the cobalt doped β-MnO2 nanoclusters displayed a prevalence of the weaker ionic bonding instead of the preferred stronger covalent bonding. This shows the limited effectiveness of cobalt as a dopant.

First-principles calculations were performed to determine the effect of Pt and Ru ternary alloying on structural, mechanical and dynamical properties of the binary Pm-3m-FeAl. FeAl based alloys are important for high-temperature applications due to their high oxygen corrosion resistance. Moreover, they are a major driver as a component for better infrastructure, industrial coating, and the improvement of automotive parts. The density functional theory (DFT) method within the generalized gradient approximation (GGA) approach was employed to perform all the calculations. The equilibrium cell parameters of the binary FeAl were predicted to be more than 90% in good agreement with the experimental data, warranting the validity of the approach employed. We found that Pt and Ru ternary alloying on FeAl significantly enhances the mechanical hardness, ductility and dynamical stability.

The B2 FeCo alloy is of great interest for high-temperature applications in the automotive industry as actuators due to its high saturation magnetization and Curie temperature. However, this alloy suffers from low ductility at room temperature. In this study, density functional theory applying the supercell approach was used to investigate the mechanical and magnetic properties of B2 Fe50Co50-XCrX (0 ≤ x ≤ 50) structures. The stability of Fe50Co50-XCrX was evaluated from the heats of formation, magnetic properties, and phonon dispersion curves. The heats of formation showed that doping with Cr enhances the thermodynamic stability of FeCo. Furthermore, the calculated Pugh and Poisson’s ratios revealed that doping with Cr effectively enhances the ductility of FeCo. Thus, the results suggest that the B2 Fe50Co50-XCrX alloy can be used for the future development of magnetic components with good strength in the automotive industry.

Monazite, as a source of raw materials, plays a significant role in the development and applications of green technologies, including medicine and energy production. It contains nuclear materials, which are challenging to extract by convectional cracking processes. However, a new method (thermal plasma cracking) has been proposed for processing monazite. The first principles calculation approach was used to investigate the theoretical structure and mechanical properties of monazite-systems to gain deeper understanding of monazite's thermodynamics and mechanical structure. The calculated lattice parameters were found to correlate well with obtained experimental values and that these monazite type systems are exceptionally mechanically stable. The results also show that there are imaginary soft modes in dispersion curves which may correspond to negative elastic constant C35 indicating vibrational instability.

Titanium is produced commercially by the Kroll process, which involves the magnesiothermic reduction of titanium tetrachloride (TiCl4). However, this is not suitable for developing a continuous reduction process. Recently, there have been attempts to develop a new continuous titanium production process by magnesiothermic reduction of other subchlorides such as titanium trichloride. In this study, the DL_POLY code was employed to investigate the influence of temperature on TiCl3 (α, β, γ). We found that the γ-phase is ordered, and all phases are spontaneous at 50 – 2000 K. The order of stability is β > α > γ, in agreement with other reported work. These findings suggest that TiCl3 might be used as a potential medium in the titanium production process.

Neodymium-based permanent magnets (Nd2Fe14B) are the potential permanent magnets for use in various applications due to their high magnetic field strength and resistance to demagnetisation. These magnets have various applications in highly efficient energy conversion machines and devices such as wind turbines and electric vehicles due to their exceptional magnetic properties. However, they suffer low operating temperatures below 585 K. In this study, we investigate the effect of Gadolinium (Gd) rare earth element on the Nd2Fe14B magnets. The structural, electronic, mechanical and vibrational properties of the magnets are calculated using the ab initio density functional theory approach. Heats of formation were used to investigate the thermodynamical stability of the magnets, where NdGdFe14B magnets are found to be thermodynamically stable. Moreover, the calculated elastic properties satisfy the tetragonal stability condition which alludes to the stability of NdGdFe14B magnets which is in agreement with the calculated eigenvalues. Furthermore, using the spin-polarized only we calculated the total magnetic moment of the NdGdFe14B magnet (59.92 μb), which is larger compared to that of Nd2Fe14B magnets. Partial substitution of Nd with Gd improves the stability and the magnetic properties of Nd2Fe14B permanent magnets.