Superconductivity of Vanadium

Wexler, Aaron; Corak, W. S.

doi:10.1103/physrev.85.85

Cited by 79 publications

(21 citation statements)

References 22 publications

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“…Kohn anomaly is characterized by electron-phonon features. Vanadium is an interesting case because this metal is one of the so-called hard superconductors (1) and it has been shown that the application of high pressure increases the superconducting temperature Tc (2, 3). The experimental phonon dispersion curves at ambient conditions in bcc phase using inelastic neutron scattering has been measured and for the longitudinal (111) branch it exhibits a dip near the (2/3 2/3 2/3) position (4).…”

mentioning

confidence: 99%

Unusual lattice dynamics of vanadium under high pressure

Luo

Ahuja

Ding

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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The electronic structures and lattice dynamics of pressure-induced complex phase transitions [bcc 3 hR1(110.5°) 3 distortedhR1(108.2°) 3 bcc] in vanadium as a function of pressure up to 400 GPa have been investigated with an ab initio method using density functional perturbation theory (DFPT). At ambient pressure, the soft transverse acoustic phonon mode corresponding to Kohn anomaly appears at a wave vector q ‫؍‬ 2k F along [00] ⌫ 3 H high symmetry direction. The nondegenerate transverse acoustic branches TA 1 on ͗1 10͘ and TA2 on ͗001͘ show an exceptionally large split at high symmetry point N (0.5 0.5 0.0). The lattice dynamical instability starts at a pressure of 62 GPa (V/V 0 ‫؍‬ 0.78, where V0 is experimental volume of bcc-V at ambient conditions), derived by phonon softening that results in phase transition of bcc 3 hR1 (alpha ‫؍‬ 110.5°). At compression around 130 GPa (V/V 0 ‫؍‬ 0.67), the rhombohedral angle of hR1 phase changed to 108.2°, and the electronic structure changed drastically. At even higher pressure, Ϸ250 GPa (V/V 0 ‫؍‬ 0.57), lattice dynamic calculations show that the bcc structure becomes stable again.ab initio calculation ͉ phonon ͉ structure phase transition A vast number of extremely interesting and fundamental physical and chemical changes in solids have been reported in high-pressure experiments. The Kohn anomaly in bcc transition metals is considered to be one of the unsolved problems in the field of high-pressure structural phase transition. Kohn anomaly is characterized by electron-phonon features. Vanadium is an interesting case because this metal is one of the so-called hard superconductors (1) and it has been shown that the application of high pressure increases the superconducting temperature Tc (2, 3). The experimental phonon dispersion curves at ambient conditions in bcc phase using inelastic neutron scattering has been measured and for the longitudinal (111) branch it exhibits a dip near the (2/3 2/3 2/3) position (4). In another experiment by Page (5), a peak in the frequency distribution for vanadium is observed at 2 ϫ 10 12 c/s, and this peak is attributed to Kohn anomalies (5). As far as calculations are concerned, the lattice dynamics study of bcc vanadium at high pressure using a full-potential linear muffin-tin orbital (LMTO) method has been performed by Suzuki and Otani (3), and these calculations show a strong change of phonon density of states with volume at 130 GPa. It has been found that the transverse acoustic phonon mode TA [00] around ϭ 1/4 shows a dramatic softening under pressure and becomes imaginary at pressures Ͼ130 GPa, indicating the possibility of a structural phase transition. Landa et al. (6) have performed the elastic constants calculations for vanadium using exact muffin-tin orbital (EMTO) and shown the trigonal shear elastic constant (C44) softening at Ϸ200 GPa due to the intraband nesting of the Fermi surface (FS).Very recently, Ding et al. (7) performed the high-pressure experiment for bcc vanadium using diamond-anvil cell and synchrotron x-ray...

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confidence: 99%

Unusual lattice dynamics of vanadium under high pressure

Luo

Ahuja

Ding

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…It also has been the subject of numerous experimental and theoretical studies due to its high superconducting transition temperature [3]. Recently, many studies [4][5][6] focused on the pure V A family elements about their elastic, dynamic, electronic, and superconducting properties el al.…”

Section: Introductionmentioning

confidence: 99%

First principles calculations of electronic properties and mechanical properties of bcc molybdenum and niobium

Liu

Shang

2011

Rare Metals

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The first principles calculations based on the density functional theory are performed to study the elastic properties and mechanical properties on Mo and Nb. It is found that the C 11 , C 12 and C 44 of metal Mo and the C 11 and C 12 of Nb are consistent with that of the experimental value and other calculated results. However, C 44 of Nb is underestimated. In order to probe the reason why the C 44 would be underestimated by theoretical calculation, we calculated the density of sated and Fermi surface of metal Nb and Mo. It is found that the most probable reason of underestimate C 44 is related to the nesting properties of the Fermi surface which produce a Van Hove singularity in the electronic density of the state closed to the Fermi level. The ideal tensile strengths along [111] direction of bcc Mo and Nb is calculated. It is found that both materials exhibit dissimilar mechanical behaviors: the stress of Nb exists a turning point at the strain 8%, which is different from the behavior of Mo.

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“…The electrical conductivity is defined by Ohm's law. J = oF (11) and is calculated from equation 9 and 8 when VT is zero (30). Klemens (28)(29)(30)35) discusses the difference in relaxation times for electrical and thermal conduction.…”

Section: Chapter II Theoretical Review Electrical and Thermal Conducmentioning

confidence: 99%

“…It is a type !! super conductor with a transition temperature that varies somewhat with purity (9)(10)(11)(12). Radebaugh earlier specific heat measurements (9,10).…”

mentioning

confidence: 91%

The thermal conductivity of high purity vanadium

Jung

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Superconductivity of Vanadium

Cited by 79 publications

References 22 publications

Unusual lattice dynamics of vanadium under high pressure

Unusual lattice dynamics of vanadium under high pressure

First principles calculations of electronic properties and mechanical properties of bcc molybdenum and niobium

The thermal conductivity of high purity vanadium

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