Ab initio calculations of elastic constants of the bcc V–Nb system at high pressures

Landa, A.; Klepeis, John E.; Söderlind, Per; Naumov, Ivan; Velikokhatnyi, Oleg I.; Vitos, Levente; Ruban, Andrei V.

doi:10.1016/j.jpcs.2006.05.027

Cited by 49 publications

(72 citation statements)

References 36 publications

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“…When comparing the band structure of RH1 to that of BCC, we find that the rhombohedral distortion splits the levels with t2g symmetry at Γ point. This effect is very similar to the Jahn-Teller distortion, and is consistent with the results of V as reported by Landa et al 15 and Ohta …”

Section: E Charge Transfer Induced Anomaliessupporting

confidence: 93%

“…For a cubic crystal, they are further reduced to only three, i.e., C11, C12 and C44. Our calculated elastic constants of Nb in BCC phase at the ground state, along with the available experimental 33 and other theoretical data, 15,16,19 are given in Table II softens at a pressure range of 20 to 150 GPa. The tetragonal shear modulus C' is also anomalously softening within the same pressure range.…”

Section: B Anomalies In Elastic Moduli At Zero Kelvinmentioning

confidence: 79%

“…It is fully consistent with the reduced shock wave experimental results 9,32 and previous theoretical data. 15 The slight deviation in the DAC data could stem from the non-hydrostaticity in the experiment or errors in the pressure scale they used. 9 This assessment validates our method, and demonstrates that our parameter setting is accurate enough for the following mechanical property study.…”

Section: A Structural Properties and Equation Of Statementioning

confidence: 99%

“…In addition, we calculate two 3D surfaces by using the Eqs. (15) and (16) (see main text), in which the distance from the origin of the coordinates to the surface equals to the Young's modulus E or the linear compressibility β in a given direction.…”

Section: B．elastic Anisotropic Characters Of Nbmentioning

confidence: 99%

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First-principles investigation of elastic anomalies in niobium at high pressure and temperature

Wang

Geng

et al. 2017

Journal of Applied Physics

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Niobium does not show any structure transition up to very high pressures. Nonetheless, by using density functional theory, we demonstrate in this work that it exhibits striking softening in elastic moduli C44 and C' at a pressure from 20 to 150 GPa. A novel anomaly softening in C44 from 275 to 400 GPa is also predicted. The physics behind these two anomalies is elaborated by electronic structure calculations, which revealed that they are actually different, with the first one directly relates to an underlying rhombohedral distortion whereas the latter originates in an electronic topological transition. The large magnitude of the softening leads to a remarkable elastic anisotropy in both the shear and the Young's moduli of Nb. Further investigation shows that thermo-electrons have an important role on these anomalies. This effect has not been noticed before. With increased electronic temperature, it is found that all anomalies (both the elastic softening and anisotropy) in Nb are gradually diminished, effectively giving rise to a temperature-induce hardening phenomenon.

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Section: E Charge Transfer Induced Anomaliessupporting

confidence: 93%

Section: B Anomalies In Elastic Moduli At Zero Kelvinmentioning

confidence: 79%

Section: A Structural Properties and Equation Of Statementioning

confidence: 99%

Section: B．elastic Anisotropic Characters Of Nbmentioning

confidence: 99%

See 2 more Smart Citations

First-principles investigation of elastic anomalies in niobium at high pressure and temperature

Wang

Geng

et al. 2017

Journal of Applied Physics

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“…Conceptually, similar phenomena have been invoked to explain the observed rhombohedral distortion that occurs in vanadium [26] and the temperature dependence of the elastic moduli of niobium [27]. However, while theory elements [28][29][30], no experiments have indicated the presence of an anomalous softening of the transverse-acoustic phonons in Ta. We show why defect generation occurs not, as might naivel bethought, simply above a critical shear stress, but at acertain stress and strain (Fig.…”

Section: Modelmentioning

confidence: 94%

Elastic-Plastic Transition under Uniaxial Stress BCC Tantalum

Guerrero¹,

Marucho²

2013

JMSE-B

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Classical molecular dynamics and lattice dynamics were utilized to study the elastic-plastic transition underuniaxial stress in defect free body center cubic (BCC) Tantalum crystals. We demonstrate that the nucleation of defects at the time scales of molecular dynamics in tantalum is due to dynamical instabilities (soft-phonons). Uniaxial compressions test were simulated along the crystallographic directions (100), (110) and (111). The results show that the nucleation of defeccts in the direction (110) is due to crystal twinning.

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Including the effects of pressure and stress in thermodynamic functions

Hammerschmidt

Abrikosov

Alfè

et al. 2013

Physica Status Solidi (b)

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This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Most applications of thermodynamic databases to materials design are limited to ambient pressure. The consideration of elastic contributions to thermodynamic stability is highly desirable but not straight-forward to realise. We present examples of existing physical models for pressure-dependent thermodynamic functions and discuss the requirements for future implementations given the existing results of experiments and first-principles calculations. We briefly summarize the calculation of elastic constants and point out examples of nonlinear variation with pressure, temperature and chemical composition that would need to be accounted for in thermodynamic databases. This is particularly the case if a system melts from different phases at different pressures. Similar relations exist between pressure and magnetism and hence set the need to also include magnetic effects in thermodynamic databases for finite pressure. We present examples to illustrate that the effect of magnetism on stability is strongly coupled to pressure, temperature, and external fields. As a further complication we discuss dynamical instabilities that may appear at finite pressure. While imaginary phonon frequencies may render a structure unstable and destroy a crystal lattice, the anharmonic effects may stabilize it again at finite temperature. Finally, we also outline a possible implementation scheme for strain effects in thermodynamic databases.

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Ab initio calculations of elastic constants of the bcc V–Nb system at high pressures

Cited by 49 publications

References 36 publications

First-principles investigation of elastic anomalies in niobium at high pressure and temperature

First-principles investigation of elastic anomalies in niobium at high pressure and temperature

Elastic-Plastic Transition under Uniaxial Stress BCC Tantalum

Including the effects of pressure and stress in thermodynamic functions

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