Elastic, thermal and structural properties of platinum (original) (raw)
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High-pressure melting curve of platinum from ab initio Z method
Physical Review B, 2012
Pt is widely used as a standard in high-pressure high-temperature experiments. The available experimental and theoretical data on Pt thermal stability is not consistent. We address the issue of high-pressure Pt melting by ab initio molecular dynamics. We demonstrate a remarkable consistency of our computed melting curve with the experimental data by N. R. Mitra, D. L. Decker, and H. B. Vanfleet [Phys. Rev. 161, 613 (1967)]. The extrapolation of their data, based on the Simon equation, nearly coincides with our ab initio computed melting curve. We propose the Pt melting curve in the form P m (kbar) = 443.0[(T /T m) 1.14 − 1].
Revista de Metalurgia, 2015
In order to broaden future application of products based on platinum and palladium a comparative analysis of their high-temperature mechanical properties was performed. Platinum and palladium are of great importance and are widely used in chemical industry, electronics, for making laboratory dishes, to name a few. Mechanical properties of pure metals, such as: tensile strength, creep rate and rupture time were investigated using universal testing machine for tensile testing of materials. Microstructure of samples was investigated by optical microscopy. Based on obtained results it can be concluded that the platinum, compared to palladium, is superior for high-temperature applications.
Solid State Communications, 2018
Ab-initio calculations based on density functional theory have been performed to study the structural, electronic, thermodynamic and mechanical properties of intermetallic compounds Pt 3 Sc and Pt 3 Y using the full-potential linearized augmented plane wave(FP-LAPW) method. The total energy calculations performed for L1 2 , D0 22 and D0 24 structures confirm the experimental phase stability. Using the generalized gradient approximation (GGA), the values of enthalpies formation are À1.23 eV/atom and À1.18 eV/atom for Pt 3 Sc and Pt 3 Y, respectively. The densities of states (DOS) spectra show the existence of a pseudo-gap at the Fermi level for both compounds which indicate the strong spd hybridization and directing covalent bonding. Furthermore, the density of states at the Fermi level N(E F), the electronic specific heat coefficient (γ ele) and the number of bonding electrons per atom are predicted in addition to the elastic constants (C 11 , C 12 and C 44). The shear modulus (G H), Young's modulus (E), Poisson's ratio (ν), anisotropy factor (A), ratio of B/G H and Cauchy pressure (C 12-C 44) are also estimated. These parameters show that the Pt 3 Sc and Pt 3 Y are ductile compounds. The thermodynamic properties were calculated using the quasi-harmonic Debye model to account for their lattice vibrations. In addition, the influence of the temperature and pressure was analyzed on the heat capacities (C p and C v), thermal expansion coefficient (α), Debye temperature (θ D) and Grüneisen parameter (γ).
Lattice Dynamical Study of Platinum by Use of van der Waals Three Body Force Shell Model
Johnson Matthey Technology Review
In present article author considered the lattice dynamical study of platinum by use of van der Waals three body force shell model [VTBFSM] due to high stiffness constant C11 and C12 . The present model uses with the frequencies of the optical and vibrational branches in the direction [100] and phonon density of states.The study of phonon spectra are important in determining the mechanica1, electrical and thermodynamical properties of elements and their alloys. The present model incorporates the effect of (VWI) and (TBI) into the rigid shell model with fcc structure, operative up to the second neighbors in short range interactions. The available measured data for platinum (Pt) well agrees with our results.
Molecular dynamics simulation of platinum film growth based on thermal evaporation method
IOP Conference Series: Materials Science and Engineering, 2019
Platinum film growth using thermal evaporation method was studied using molecular dynamics simulation. This platinum film was intended as catalyst film for graphene growth. Tersoff, Eam and Lennard-Jones potential were used to describe interaction of Si-Si, Pt-Pt and Pt-Si respectively. Deposition process was performed with low incident energy to represent thermal evaporation method. Our simulation found that heating temperature at 400 K produced platinum film with higher percentage of crystal structure than other heating condition 300K, 500K & 600K. We also found transition phase from fcc to bcc at 600K.
A molecular-dynamics study of thermal and physical properties of platinum nanoclusters
Fluid Phase Equilibria, 2009
Metallic nanoclusters are interesting because of their utility in catalysis and sensors. The thermal and physical characteristics of metallic Pt nanoclusters with different sizes were investigated via moleculardynamics simulations using Quantum Sutton-Chen (QSC) potential. This force field accurately predicts solid and liquid states properties as well as melting of the bulk platinum. Molecular dynamic simulations of Pt nanoclusters with 256, 456, 500, 864, 1372, 2048, 2916, 4000, 5324, 6912, 8788 atoms have been carried out at various temperatures. The Pt-Pt radial distribution function, internal energy, heat capacity, enthalpy, entropy of the nanoclusters were calculated at some temperatures. These properties are used to characterize the physical phase and also to determine the melting transition of each nanocluster. The melting point predicted by the various properties is consistent with each other and shows that the melting temperature increases with the particle size, approaching to the bulk limit for the largest one. The size dependence of the melting point has been reported, both experimentally and theoretically for the atomic nanoclusters. We have found that the melting of the platinum nanoclusters commences at the surface and the relation T m,N = T m,bulk −˛N −1/3 between the melting point of nanocluster (T m,N ) and that of the bulk (T m,bulk ) holds. The extrapolation of T m,N versus N −1/3 gives T m,bulk = 2058.1 K which is in a good agreement with the experimental value of 2041 K.
Thermodynamics of small platinum clusters
Computational materials science, 2006
Using the Voter and Chen version of an embedded atom model, derived by fitting simultaneously to experimental data of both the diatomic molecule and bulk platinum, we have studied the melting behavior of free, small platinum clusters in the size range of N = 15–19 in the molecular dynamics simulation technique. We present an atom-resolved analysis method that includes physical quantities such as the root-mean-square bond-length fluctuation and coordination number for individual atoms as functions of temperature. The results show that as the Pt15–Pt18 clusters exhibit multistage melting, melting in Pt19 cluster takes place in a single but interesting stage. None of these melting stages occurs at a specific temperature, rather, melting processes take place over a finite temperature range. This range is larger for less symmetric clusters. An ensemble of clusters in the melting region is a mixture of different isomeric forms of the clusters. The multistage melting and the occurrence of a single melting stage over a temperature range are two different phenomena.
In situ characterization of the high pressure – high temperature melting curve of platinum
Scientific Reports, 2019
In this work, the melting line of platinum has been characterized both experimentally, using synchrotron X-ray diffraction in laser-heated diamond-anvil cells, and theoretically, using ab initio simulations. In the investigated pressure and temperature range (pressure between 10 GPa and 110 GPa and temperature between 300 K and 4800 K), only the face-centered cubic phase of platinum has been observed. The melting points obtained with the two techniques are in good agreement. Furthermore, the obtained results agree and considerably extend the melting line previously obtained in large-volume devices and in one laser-heated diamond-anvil cells experiment, in which the speckle method was used as melting detection technique. The divergence between previous laser-heating experiments is resolved in favor of those experiments reporting the higher melting slope.
Ab-initio study of several static and dynamic properties of liquid palladium and platinum
EPJ Web of Conferences, 2017
We report a study on several static and dynamic properties of liquid Pd and Pt metals at thermodynamic conditions near their respective triple points. The calculations have been carried out by an ab initio molecular dynamics simulation technique. Results are reported for several static structural magnitudes which are compared with the available X-ray diraction. As for the dynamic properties, results have been obtained for both single and collective dynamical magnitudes as well as for some transport coecients which are compared with the corresponding experimental data.