The self-consistent ab initio lattice dynamical method

Souvatzis, Petros; Eriksson, Olle; Katsnelson, M. I.; Rudin, Sven P.

doi:10.1016/j.commatsci.2008.06.016

Cited by 123 publications

(119 citation statements)

References 20 publications

Supporting

Mentioning

116

Contrasting

Order By: Relevance

“…For these volumes, the bcc stability is determined by computing the phonon dispersions as functions of temperature using the SCAILD method. This approach is described in great detail [13] and not repeated here, but the general idea is to account for thermal vibrations of the atoms and their interactions. This is accomplished by (i): calculating the forces on atoms, displaced from the ideal bcc positions according to the temperature, and (ii): computing the phonon dispersions.…”

Section: Computational Detailsmentioning

confidence: 99%

Ab initiophase stability at high temperatures and pressures in the V-Cr system

2014

View full text Add to dashboard Cite

The phase stability of vanadium metal and vanadium-chromium alloys at high temperatures and pressures is explored by means of first-principles electronic-structure calculations. Utilizing the self-consistent ab initio lattice dynamics (SCAILD) approach in conjunction with density-functional theory, we show that pressure-induced mechanical instability of body-centered cubic vanadium metal, which results in formation of a rhombohedral phase at around 60-70 GPa at room temperatures, will prevail significant heating and compression. Furthermore, alloying with chromium decreases the temperature at which stabilization of the body-centered cubic phase occurs at elevated pressure.2

show abstract

Section: Computational Detailsmentioning

confidence: 99%

Ab initiophase stability at high temperatures and pressures in the V-Cr system

2014

View full text Add to dashboard Cite

show abstract

“…This self-consistent ab initio lattice dynamics (SCAILD) technique 7 has been used to investigate the hightemperature bcc phase of several metals including Ti, Zr, Hf, and even iron 8 . The approach has been described in detail 9 and has heretofore utilized ab initio forces obtained from the projector augmented wave (PAW) method in conjunction with the currently most robust PAW implementation, the Vienna ab initio simulation package (vasp) 10 . This method allows for efficient evaluation of the forces required for the SCAILD scheme while being adequately accurate for several transition metals.…”

Section: -Uranium From Relativistic First-principles Theorymentioning

confidence: 99%

“…In particular, we choose to extract forces from (electronic) free-energy shifts due to small atomic displacements. The SCAILD scheme requires forces on all atoms in a supercell for which the atoms are thermally displaced from the perfect bcc lattice positions 9 . We obtain these forces by independently moving each atom a small amount (± 0.2% of lattice constant) along the x, y, and z Cartesian axis, least-square fitting a second order polynomial to the free energies and extracting the force component along the considered axis.…”

Section: -Uranium From Relativistic First-principles Theorymentioning

confidence: 99%

High-temperature phonon stabilization ofγ-uranium from relativistic first-principles theory

et al. 2012

Self Cite

View full text Add to dashboard Cite

A microscopic explanation for temperature stabilization of the body-centered cubic (bcc) phase in the actinide metals is proposed. We show that for a prototype actinide, uranium, phonon-phonon interaction promotes bcc γ-U when heated even though at low temperatures it is mechanically a strongly unstable phase. Utilizing the recently developed self-consistent ab initio lattice dynamics (SCAILD) scheme in conjunction with highly accurate and fully relativistic density functional theory we obtain phonon dispersion and density of states that compare well with data acquired from inelastic neutron-scattering experiments. The investigation thus establishes that high-temperature lattice dynamics can be modeled from ab initio theory even for complex materials with substantial electron correlation including the actinides. PACS numbers:Density-functional theory (DFT) 1 has proven to be remarkably successful in describing the T = 0 K groundstate phases of most metals. Skriver 2 showed that it predicts the correct ground-state crystal structure for many transition elements when applied in a spherical linear muffin-tin orbital technique. Later 3 it became evident that DFT -implemented in more sophisticated methods appropriately treating complex crystal structures-also confirms the ground-state phases of the actinides. Except for metals with strong electron-correlation effects, such as the rare-earths, the DFT workhorse can nowadays be effectively used throughout the Periodic Table of Elements for low-temperature condensed-matter applications.There has been a long-standing difficulty, however, to model high-temperature phases with an accuracy analogous to that of the ground state at room or lower temperatures. The reason is that treating electronic and vibrational interactions simultaneously within a quantum-mechanical framework is a daunting task. It becomes particularly problematic when the high-temperature phase is mechanically unstable at low temperatures thus ruling out the typically applied perturbation theory of the zero-temperature electronic structure. An additional and potentially serious pitfall, when studying f -electron systems such as the actinide or rare-earth metals, is the possibility of a dramatic change in the f -electron behavior with temperature. For instance, cerium metal has a temperature-driven (α → γ) phase transition that has been argued to be caused by localization (Mott transition) 4 where the f states are removed from the Fermi level (highest occupied energy). Similarly, uranium (or any other actinide metal) could exhibit a localization of the 5f shell at elevated temperatures that cannot be addressed within conventional DFT. Localization is consistent with the formation of a high-symmetry phase such as bcc in U (see below) but because there is no significant volume expansion, often observed during this type of transition, we have reason to believe that this difficult-to-model mechanism is not present in this case. It was also shown that localization did not play a role in stabilizing bcc in Pu 5 ,...

show abstract

“…SCAILD has addressed elemental metals but never before alloy systems. The approach is described in great detail [13] and not repeated here, but the general idea is to account for thermal vibrations of the atoms and their interactions. This is accomplished by (i): calculating the forces on atoms, displaced from the ideal bcc positions according to the temperature, and (ii): computing the phonon density of states (DOS).…”

Section: Introductionmentioning

confidence: 99%

First-principles phase stability in the Ti-V alloy system

Söderlind

Landa

Yang

et al. 2013

Journal of Alloys and Compounds

View full text Add to dashboard Cite

Phase stability in the transition metals are mostly dictated by the bonding of the d electrons and is believed to be fairly well understood from either a canonical-band picture or a tight-binding model. These models are related and capture the fact that as one proceeds through the nonmagnetic d-transition series one encounters the hexagonal closepacked (hcp), body-centered cubic (bcc), hcp, and face-centered cubic (fcc) phases. This structural sequence depends on the gradual filling of the d band (roughly one electron per atomic number increase) that is altered when magnetism is present simply due to the spin polarization of the d band. However, recent more careful experimental and theoretical studies have shown that the aforementioned appealing models do not entirely explain the bonding and phase stability in the transition metals. First, there is a destabilization of the bcc phase due to pressure in the Group Vb metals (V, Nb, and Ta) and second, a temperature-induced stabilization of the bcc phase in the Group IVb (Ti, Zr, and Hf) metals even though at low temperatures it is strongly unstable. Here we address the latter phenomenon and study the influence of alloying titanium with its next neighbor vanadium by applying the recently developed self-consistent ab initio lattice dynamics (SCAILD) approach that has heretofore never been utilized for an alloy system.

show abstract

The self-consistent ab initio lattice dynamical method

Cited by 123 publications

References 20 publications

Ab initiophase stability at high temperatures and pressures in the V-Cr system

Ab initiophase stability at high temperatures and pressures in the V-Cr system

High-temperature phonon stabilization ofγ-uranium from relativistic first-principles theory

First-principles phase stability in the Ti-V alloy system

Contact Info

Product

Resources

About