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HfTi_BCC_SolidSolution_128atoms_VASP6

We performed density functional theory (DFT) calculations for body-centered-cubic (BCC) structures with 128 lattices sites of solid solution binary alloys hafnium-titanium (Hf-Ti). The electronic structures of alloys have been calculated using Vienna Ab initio Simulation Package (VASP). Within this package the DFT approach is used to reduce many-body Schrodinger equation to set of single particle Kohn-Sham (KS) equations. The generalized electronic exchange-correlation functional is described by generalized gradient approximation with the Perdew-Burke-Ernzerhof parametrization. The electron-ion interactions is described by pseudopotentials developed within the plane-wave basis projector augmented-wave (PAW) approach. These pseudopotentials are available at the VASP portal (http://cms.mpi.univie.ac.at/vasp/). Our calculations have been run with the pseudopotentials treating s and p semi-core states as valence in case for the elements Hf and Ti. The electronic densities and potentials are expanded over plane-waves with energy cutoff of 350 eV. 2x2x2 k-mesh and normal precision were used. The alloys were modeled by supercell containing 128 randomly distributed atoms. At initial step the atoms occupy perfect bcc lattice cites. This initial structure was optimized until energy changes less than 1e-6 eV, while forces acting on atoms don't exceed 1e-2 eV/angstrom. The electron-ion interaction is described by PAW pseudopotentials. The calculations have been collected by sampling chemical compositions across the entire compositional range. The chemical compositions have been sampled by progressively changing the number of atoms per constituent by 4. For each chemical composition of binaries and ternaries, the first-principle calculations have been run for 100 randomized arrangements of the constituents on the BCC lattice sites. We collected data for a total of 3,100 randomized atomic structures over 31 chemical compositions. The calculations have been collected on Air Force HPC11 cluster using the VASP 6.5.1. Additional methodology and file structure information is available in the dataset README.txt file.

36 MATERIALS SCIENCE↗

An Overview of Nano Multilayers as Model Systems for Developing Nanoscale Microstructures

The microstructural transformations of binary nanometallic multilayers (NMMs) to equiaxed nanostructured materials were explored by characterizing a variety of nanoscale multilayer films. Four material systems of multilayer films, Hf-Ti, Ta-Hf, W-Cr, and Mo-Au, were synthesized by magnetron sputtering, heat treated at 1000 °C, and subsequently characterized by transmission electron microscopy. Binary systems were selected based on thermodynamic models predicting stable nanograin formation with similar global compositions around 20–30 at.%. All NMMs maintained nanocrystalline grain sizes after evolution into an equiaxed structure, where the systems with highly mobile incoherent interfaces or higher energy interfaces showed a more significant increase in grain size. Furthermore, varying segregation behaviors were observed, including grain boundary (GB) segregation, precipitation, and intermetallic formation depending on the material system selected. The pathway to tailored microstructures was found to be governed by key mechanisms and factors as determined by a film’s initial characteristics, including global and local composition, interface energy, layer structure, and material selection. This work presents a global evaluation of NMM systems and demonstrates their utility as foundation materials to promote tailored nanomaterials.

Appleget, Chelsea D.↗

Materials Data on HfTi3 by Materials Project

HfTi3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded to twelve Ti atoms to form HfTi12 cuboctahedra that share corners with six equivalent HfTi12 cuboctahedra, corners with twelve TiHf4Ti8 cuboctahedra, edges with eighteen TiHf4Ti8 cuboctahedra, faces with eight equivalent HfTi12 cuboctahedra, and faces with twelve TiHf4Ti8 cuboctahedra. There are six shorter (2.98 Å) and six longer (3.01 Å) Hf–Ti bond lengths. There are two inequivalent Ti sites. In the first Ti site, Ti is bonded to four equivalent Hf and eight Ti atoms to form distorted TiHf4Ti8 cuboctahedra that share corners with four equivalent HfTi12 cuboctahedra, corners with fourteen TiHf4Ti8 cuboctahedra, edges with six equivalent HfTi12 cuboctahedra, edges with twelve TiHf4Ti8 cuboctahedra, faces with four equivalent HfTi12 cuboctahedra, and faces with sixteen TiHf4Ti8 cuboctahedra. There are a spread of Ti–Ti bond distances ranging from 2.91–3.11 Å. In the second Ti site, Ti is bonded to four equivalent Hf and eight equivalent Ti atoms to form distorted TiHf4Ti8 cuboctahedra that share corners with four equivalent HfTi12 cuboctahedra, corners with fourteen TiHf4Ti8 cuboctahedra, edges with six equivalent HfTi12 cuboctahedra, edges with twelve equivalent TiHf4Ti8 cuboctahedra, faces with four equivalent HfTi12 cuboctahedra, and faces with sixteen TiHf4Ti8 cuboctahedra.

36 MATERIALS SCIENCE↗

Materials Data on HfTi by Materials Project

HfTi crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Hf is bonded to six equivalent Hf and six equivalent Ti atoms to form distorted HfHf6Ti6 cuboctahedra that share corners with eighteen equivalent HfHf6Ti6 cuboctahedra, edges with six equivalent HfHf6Ti6 cuboctahedra, edges with twelve equivalent TiHf6Ti6 cuboctahedra, faces with eight equivalent HfHf6Ti6 cuboctahedra, and faces with twelve equivalent TiHf6Ti6 cuboctahedra. All Hf–Hf bond lengths are 3.09 Å. All Hf–Ti bond lengths are 3.01 Å. Ti is bonded to six equivalent Hf and six equivalent Ti atoms to form distorted TiHf6Ti6 cuboctahedra that share corners with eighteen equivalent TiHf6Ti6 cuboctahedra, edges with six equivalent TiHf6Ti6 cuboctahedra, edges with twelve equivalent HfHf6Ti6 cuboctahedra, faces with eight equivalent TiHf6Ti6 cuboctahedra, and faces with twelve equivalent HfHf6Ti6 cuboctahedra. All Ti–Ti bond lengths are 3.09 Å.

36 MATERIALS SCIENCE↗