First-Principles Investigation of the Effect of Solutes on the Ideal Shear Resistance and Electronic Properties of Magnesium
01 Jan 2019-pp 231-237
TL;DR: In this article, the effects of various alloying elements on ideal shear resistance (ISR) across different slip systems of Mg were investigated using first-principles calculations.
Abstract: Solute addition is an effective way to enhance mechanical properties, especially in magnesium based alloys due to the limited number of slip systems available for deformation at the room temperature. Hence, the effects of various alloying elements on ideal shear resistance (ISR) across different slip systems of Mg were investigated using first-principles calculations. The addition of a Ce, Y, or Zr solute atom was found to decrease ISR, whereas the substitution of a Sn, Li, Al, or Zn atom increased the ISR of Mg. The most active slip system in Mg changed from the basal partial (0001)\( \left[ {10\bar{1}0} \right] \) to prismatic \( (10\bar{1}0)[11\bar{2}0] \) upon substitution of a Ce, Y, or Zr solute atom, whereas the addition of Sn, Li, Al, or Zn solute atom had negligible effect on the plastic anisotropy. Furthermore, the electronic density of states and valence charge transfer provides a quantum insight into the underlying factors influencing the observed softening/strengthening behavior. For instance, the electronic density of states calculation shows that the contribution from d states of Ce, Y, and Zr solute atoms decreases the electronic structure stability of their respective solid solution, thereby enhancing slip activities. Theoretical analyses were also performed, and a shearability parameter was introduced to understand the implications of the observed variation in ideal shear resistance on the macroscopic behavior of Mg alloys.
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IBM1
TL;DR: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way and can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function.
Abstract: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way. The method allows high-quality first-principles molecular-dynamics calculations to be performed using the original fictitious Lagrangian approach of Car and Parrinello. Like the LAPW method it can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function. The augmentation procedure is generalized in that partial-wave expansions are not determined by the value and the derivative of the envelope function at some muffin-tin radius, but rather by the overlap with localized projector functions. The pseudopotential approach based on generalized separable pseudopotentials can be regained by a simple approximation.
61,450 citations
TL;DR: In this article, the tetrahedron method was used for Brillouin-zone integrations and a translational grid of k points and tetrahedral elements was proposed to obtain results for insulators identical to those obtained with special-point methods with the same number of points.
Abstract: Several improvements of the tetrahedron method for Brillouin-zone integrations are presented. (1) A translational grid of k points and tetrahedra is suggested that renders the results for insulators identical to those obtained with special-point methods with the same number of k points. (2) A simple correction formula goes beyond the linear approximation of matrix elements within the tetrahedra and also improves the results for metals significantly. For a required accuracy this reduces the number of k points by orders of magnitude. (3) Irreducible k points and tetrahedra are selected by a fully automated procedure, requiring as input only the space-group operations. (4) The integration is formulated as a weighted sum over irreducible k points with integration weights calculated using the tetrahedron method once for a given band structure. This allows an efficient use of the tetrahedron method also in plane-wave-based electronic-structure methods.
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TL;DR: In this paper, the authors proposed a pseudowave function inside the cut-off radius with the concept of ultrasoft pseudopotentials introduced by Vanderbilt optimal compromise between transferability and plane-wave convergence.
Abstract: The construction of accurate pseudopotentials with good convergence properties for the first-row and transition elements is discussed. We show that by combining an improved description of the pseudowavefunction inside the cut-off radius with the concept of ultrasoft pseudopotentials introduced by Vanderbilt optimal compromise between transferability and plane-wave convergence can be achieved. With the new pseudopotentials, basis sets with no more than 75-100 plane waves per atom are sufficient to reproduce the results obtained with the most accurate norm-conserving pseudopotentials.
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TL;DR: With a density of 1.74 g/cm3—about 30% less than aluminum, one-quarter that of steel, and nearly the same as many polymers—magnesium is attractive for lightweight structural systems and, most notably, automotive systems.
Abstract: The compelling need for lightweight, energy-efficient, environmentally benign engineering systems is driving the development of a wide range of structural and functional materials for energy generation, energy storage, propulsion, and transportation. These challenges motivate wider spread use of magnesium—the eighth most common element in the earth's crust and also extractable from seawater. In addition, the ease of recycling, compared with polymers, makes magnesium alloys environmentally attractive. Importantly, with a density of 1.74 g/cm3—about 30% less than aluminum, one-quarter that of steel, and nearly the same as many polymers—magnesium is attractive for lightweight structural systems and, most notably, automotive systems. A typical car weighing 1525 kg currently contains about 975 kg of steel, 127 kg of Al, 114 kg of polymeric materials, and 5 to 6 kg of magnesium ( 1 ). It is estimated that 22.5 kg of mass reduction would improve fuel efficiency by around 1%; thus, automotive manufacturers worldwide have goals to increase the Mg content of automobiles to between 45 and 160 kg ( 1 , 2 ).
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