scholarly journals Pseudopotential Calculations of the Band Structure and Fermi Surface of Mercury

1972 ◽  
Vol 50 (14) ◽  
pp. 1659-1675 ◽  
Author(s):  
J. C. Jones ◽  
W. R. Datars
Keyword(s):  
Fermi Surface ◽  
Fermi Energy ◽  
Outer Core ◽  
Projection Operators ◽  
Energy Bands ◽  
Nonlocal Operators ◽  
Pseudopotential Theory ◽  
Pseudopotential Calculations ◽  
Repulsive Potentials ◽  
Semi Empirical

Semi-empirical local and nonlocal pseudopotentials have been used to calculate the energy bands and Fermi surface of crystalline mercury. The nonlocal pseudopotentials were an approximation in which the repulsive potentials of the outer core states were explicitly represented by nonlocal projection operators. A search in parameter space revealed three separate regions in which the Fermi surface generated by the pseudopotential was a good fit to experimental magneto-acoustic calipers and extremal sectional areas. One of the regions investigated was equivalent to the Animalu–Heine pseudopotential for mercury and a second was very similar to the Evans pseudopotential which has been used for liquid mercury. Although there were strong resemblances in the band structures generated by the different classes of pseudopotential, the symmetry characteristics of the bands were different. The nonlocal operators had a strong influence on the Fermi energy with p-like and d-like operators causing an increase in the Fermi energy. The influence of spin–orbit coupling and more general questions of pseudopotential theory and band symmetry were also considered.

Self-consistent energy bands and Fermi surface of YZn

1977 ◽  
Vol 7 (7) ◽  
pp. 1229-1244 ◽  
Author(s):  
A Hasegawa ◽  
A Yanase
Keyword(s):  
Fermi Surface ◽  
Energy Bands ◽  
Self Consistent

Transfer Integrals and Band Structures in (Et)2X Salts

1989 ◽  
Vol 173 ◽  
Author(s):  
Oliver H. Leblanc ◽  
Margaret L. Blohm ◽  
Richard P. Messmer
Keyword(s):  
Low Temperature ◽  
Nearest Neighbor ◽  
Spherical Wave ◽  
Tight Binding ◽  
Ab Initio Method ◽  
Energy Bands ◽  
Hubbard Hamiltonian ◽  
Transfer Integrals ◽  
Semi Empirical ◽  
Very Low Temperature

ABSTRACTTransfer integrals (tij) between pairs of nearest neighbor ET molecules were calculated by an ab initio method. Tight-binding one-electron energy bands constructed from the tij are similar to those previously calculated by Mori and by Whangbo and their coworkers by semi-empirical, extended Hückel methods, but quite different from those found by Kübler et al. in β-(ET)2I3 using the augmented spherical wave (ASW) method. However, all these band models are suspect. The Hubbard on-site repulsion parameter U is estimated to be about twice the band widths, indicating that a full treatment of the Hubbard hamiltonian is needed. Also, polaron effects appear to control transport except at very low temperature.

The Shubnikov – de Haas effect in dilute lead-in-bismuth alloys

1968 ◽  
Vol 46 (21) ◽  
pp. 2413-2423 ◽  
Author(s):  
On-Ting Woo ◽  
R. J. Balcombe
Keyword(s):  
Band Structure ◽  
Fermi Surface ◽  
Carrier Concentration ◽  
Fermi Energy ◽  
Dilute Alloys ◽  
Haas Effect ◽  
Effect Of Alloying

The differential Shubnikov – de Haas effect has been studied in samples of bismuth containing up to 50 parts per million of lead. The results indicate that the only effect of alloying on the band structure of bismuth is to shift the Fermi energy; the sizes of the various pieces of the Fermi surface are changed, but their shapes are not distorted. The ratio of the change in net carrier concentration to the concentration of lead atoms is found to be only 0.4, which is anomalously low, compared with values of about 1.0 found for dilute alloys of other metals in bismuth.

scholarly journals Lifshitz transitions and zero point lattice fluctuations in sulfur hydride showing near room temperature superconductivity

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Antonio Bianconi ◽  
Thomas Jarlborg
Keyword(s):  
Critical Temperature ◽  
Fermi Surface ◽  
Fermi Energy ◽  
Room Temperature ◽  
Zero Point ◽  
Shape Resonance ◽  
Eliashberg Theory ◽  
Lifshitz Transitions ◽  
Point Lattice ◽  
Lattice Fluctuations

AbstractEmerets’s experiments on pressurized sulfur hydride have shown that H3S metal has the highest known superconducting critical temperature Tc = 203 K. The Emerets data show pressure induced changes of the isotope coefficient between 0.25 and 0.5, in disagreement with Eliashberg theory which predicts a nearly constant isotope coefficient.We assign the pressure dependent isotope coefficient to Lifshitz transitions induced by pressure and zero point lattice fluctuations. It is known that pressure could induce changes of the topology of the Fermi surface, called Lifshitz transitions, but were neglected in previous papers on the H3S superconductivity issue. Here we propose thatH3S is a multi-gap superconductor with a first condensate in the BCS regime (located in the large Fermi surface with high Fermi energy) which coexists with second condensates in the BCS-BEC crossover regime (located on the Fermi surface spots with small Fermi energy) near the and Mpoints.We discuss the Bianconi-Perali-Valletta (BPV) superconductivity theory to understand superconductivity in H3S since the BPV theory includes the corrections of the chemical potential due to pairing and the configuration interaction between different condensates, neglected by the Eliashberg theory. These two terms in the BPV theory give the shape resonance in superconducting gaps, similar to Feshbach resonance in ultracold fermionic gases, which is known to amplify the critical temperature. Therefore this work provides some key tools useful in the search for new room temperature superconductors.

Energy Bands and Fermi Surface of Scandium

1968 ◽  
Vol 173 (3) ◽  
pp. 685-688 ◽  
Author(s):  
G. S. Fleming ◽  
T. L. Loucks
Keyword(s):  
Fermi Surface ◽  
Energy Bands

Energy Bands and Fermi Surface of OrderedβBrass

1969 ◽  
Vol 186 (3) ◽  
pp. 609-618 ◽  
Author(s):  
F. J. Arlinghaus
Keyword(s):  
Fermi Surface ◽  
Energy Bands
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