Superconductivity and Electronic Structure of Perovskite MgCNi3

The electronic structure, stability, electron phonon coupling and superconductivity of the non-oxide perovskite MgCNi$_3$ are studied using density functional calculations. The band structure is dominated by a Ni $d$ derived density of states peak just below the Fermi energy, which leads to a moderate Stoner enhancement, placing MgCNi$_3$ in the range where spin fluctuations may noticeably affect transport, specific heat and superconductivity, providing a mechanism for reconciling various measures of the coupling $\lambda$. Strong electron phonon interactions are found for the octahedral rotation mode and may exist for other bond angle bending modes. The Fermi surface contains nearly cancelling hole and electron sheets that give unusual behavior of transport quantities particularly the thermopower. The results are discussed in relation to the superconductivity of MgCNi$_3$.Comment: 4 pages, RevTex, 5 ps figure

Screened Coulomb interactions in metallic alloys: I. Universal screening in the atomic sphere approximation

We have used the locally self-consistent Green's function (LSGF) method in supercell calculations to establish the distribution of the net charges assigned to the atomic spheres of the alloy components in metallic alloys with different compositions and degrees of order. This allows us to determine the Madelung potential energy of a random alloy in the single-site mean field approximation which makes the conventional single-site density-functional- theory coherent potential approximation (SS-DFT-CPA) method practically identical to the supercell LSGF method with a single-site local interaction zone that yields an exact solution of the DFT problem. We demonstrate that the basic mechanism which governs the charge distribution is the screening of the net charges of the alloy components that makes the direct Coulomb interactions short-ranged. In the atomic sphere approximation, this screening appears to be almost independent of the alloy composition, lattice spacing, and crystal structure. A formalism which allows a consistent treatment of the screened Coulomb interactions within the single-site mean-filed approximation is outlined. We also derive the contribution of the screened Coulomb interactions to the S2 formalism and the generalized perturbation method.Comment: 28 pages, 8 figure

Static and dynamic structure factors with account of the ion structure for high-temperature alkali and alkaline earth plasmas

The electron-electron, electron-ion, ion-ion and charge-charge static structure factors are calculated for alkali (at T = 30 000 K, 60 000 K, n (e) = 0.7 x 10(21) A center dot 1.1 x 10(22) cm(-3)) and Be2+ (at T = 20 eV, n (e) = 2.5 x 10(23) cm(-3)) plasmas using the method described by Gregori et al. The dynamic structure factors for alkali plasmas are calculated at T = 30 000 K, n (e) = 1.74 x 10(20), 1.11 x 10(22) cm(-3) using the method of moments developed by Adamjan et al. In both methods the screened Hellmann-Gurskii-Krasko potential, obtained on the basis of Bogolyubov's method, has been used taking into account not only the quantum-mechanical effects but also the repulsion due to the Pauli exclusion principle. The repulsive part of the Hellmann-Gurskii-Krasko (HGK) potential reflects important features of the ion structure. Our results on the static structure factors for Be2+ plasma deviate from the data obtained by Gregori et al., while our dynamic structure factors are in a reasonable agreement with those of Adamyan et al.: at higher values of k and with increasing k the curves damp down while at lower values of k, and especially at higher electron coupling, we observe sharp peaks also reported in the mentioned work. For lower electron coupling the dynamic structure factors of Li+, Na+, K+, Rb+ and Cs+ do not differ while at higher electron coupling these curves split. As the number of shell electrons increases from Li+ to Cs+ the curves shift in the direction of low absolute value of omega and their heights diminish. We conclude that the short range forces, which we take into account by means of the HGK model potential, which deviates from the Coulomb and Deutsch ones, influence the static and dynamic structure factors significantly.The work has been realised at the Humboldt University at Berlin (Germany). One of the authors (S. P. Sadykova) would like to express sincere thanks to the Erasmus Mundus Program of the EU for the financial support and especially to Mr. M. Parske for his aid, to the Institute of Physics, Humboldt University at Berlin, for the support which made her participation at some scientific Conferences possible; I. M. T. acknowledges the financial support of the Spanish Ministerio de Educacion y Ciencia Project No. ENE2007-67406-C02-02/FTN and valuable discussions with Dr. D. Gericke.Sadykova, SP.; Ebeling, W.; Tkachenko Gorski, IM. (2011). Static and dynamic structure factors with account of the ion structure for high-temperature alkali and alkaline earth plasmas. European Physical Journal D. 61(1):117-130. https://doi.org/10.1140/epjd/e2010-10118-yS117130611G. Gregori, O.L. Landen, S.H. Glenzer, Phys. Rev. E 74, 026402 (2006)G. Gregori, A. Ravasio, A. Höll, S.H. Glenzer, S.J. Rose, High Energy Density Physics 3, 99 (2007)V.M. Adamyan, I.M. Tkachenko, Teplofiz. Vys. Temp. 21, 417 (1983) [High Temp. (USA) 21, 307 (1983)]V.M. Adamyan, T. Meyer, I.M. Tkachenko, Fiz. Plazmy 11, 826 (1985) [Sov. J. Plasma Phys. 11, 481 (1985)]S.V. Adamjan, I.M. Tkachenko, J.L. Muñoz-Cobo, G. Verdú Martín, Phys. Rev. E 48, 2067 (1993)V.M. Adamyan, I.M. Tkachenko, Contrib. Plasma Phys. 43, 252 (2003)S. Sadykova, W. Ebeling, I. Valuev, I. Sokolov, Contrib. Plasma Phys. 49, 76 (2009)M.J. Rosseinsky, K. Prassides, Nature 464, 39 (2010)Physics and Chemistry of Alkali Metal Adsorption, edited by H.P. Bonzel, A.M. Bradshaw, G. Ertl (Elsevier, Amsterdam, 1989), Materials Science Monographs, Vol. 57A.N. Klyucharev, N.N. Bezuglov, A.A. Matveev, A.A. Mihajlov, Lj.M. Ignjatović, M.S. Dimitrijević, New Astron. Rev. 51, 547 (2007)F. Hensel, Liquid Metals, edited by R. Evans, D.A. Greenwood, IOP Conf. Ser. No. 30 (IPPS, London, 1977)F. Hensel, S. Juengst, F. Noll, R. Winter, In Localisation and Metal Insulator Transitions, edited by D. Adler, H. Fritsche (Plenum Press, New York, 1985)N.F. Mott, Metal-Insulator Transitions (Taylor and Francis, London, 1974)H. Hess, Physics of nonideal plasmas, edited by W. Ebeling, A. Foerster, R. Radtke, B.G. Teubner (Leipzig, 1992)V. Sizyuk, A. Hassanein, T. Sizyuk, J. Appl. Phys. 100, 103106 (2006)S. Sadykova, W. Ebeling, I. Valuev, I. Sokolov, Contrib. Plasma Phys. 49, 388 (2009)H. Ebert, Physikalisches Taschenbuch (F. Vieweg & Sohn, Braunschweig, 1967)S.H. Glenzer, G. Gregori, R.W. Lee, F.J. Rogers, S.W. Pollaine, O.L. Landen, Phys. Rev. Lett. 90, 175002 (2003)G. Gregori, S.H. Glenzer, H.-K. Chung, D.H. Froula, R.W. Lee, N.B. Meezan, J.D. Moody, C. Niemann, O.L. Landen, B. Holst, R. Redmer, S.P. Regan, H. Sawada, J. Quant. Spectrosc. Radiat. Transfer 99, 225237 (2006)D. Riley, N.C. Woolsey, D. McSherry, I. Weaver, A. Djaoui, E. Nardi, Phys. Rev. Lett. 84, 1704 (2000)S.H. Glenzer, Phys. Rev. Lett. 98, 065002 (2007)J. Sheffield, Plasma Scattering of Electromagnetic Radiation (Academic Press, New York, 1975)A. Höll, Th. Bornath, L. Cao, T. Döppner, S. Düsterer, E. Föster, C. Fortmann, S.H. Glenzer, G. Gregori, T. Laarmann, K.-H. Meiwes-Broer, A. Przystawik, P. Radcliffe, R. Redmer, H. Reinholz, G. Röpke, R. Thiele, J. Tiggesbäumker, S. Toleikis, N.X. Truong, T. Tschentscher, I. Ushmann, U. Zastrau, High Energy Density Phys. 3, 120 (2007)Yu.V. Arkhipov, A. Askaruly, D. Ballester, A.E. Davletov, G.M. Meirkhanova, I.M. Tkachenko, Phys. Rev. E 76, 026403 (2007)Yu.V. Arkhipov, A. Askaruly, D. Ballester, A.E. Davletov, I.M. Tkachenko, G. Zwicknagel, Phys. Rev. E 81, 026402 (2010)J.P. Hansen, I.R. Mc. Donald, Phys. Rev. A 23, 2041 (1981)J.P. Hansen, E.L. Polock, I.R. McDonald, Phys. Rev. Lett. 32, 277 (1974)V. Schwarz, B. Holst, T. Bornath, C. Fortmann, W-D. Kraeft, R. Thiele, R. Redmer, G. Gregori, H. Ja Leed, T. Döppner, S.H. Glenzer, High Energy Density Phys. 5, 1 (2009)D.O. Gericke, K. Wünsch, J. Vorberger, Nucl. Instrum. Methods Phys. Res. A 606, 142 (2009)B. Bernu, D. Ceperley, Quantum Monte Carlo Methods in Physics and Chemistry, edited by M.P. Nightingale, C. Umrigar (Kluwer Academic Publishers, Boston, 1999), NATO ASI Series, Series C, Mathematical and Physical Sciences, Vol. C-525G. Kelbg, Ann. Physik 13 354 (1964)C. Deutsch, Phys. Lett. A 60, 317 (1977)H. Minoo, M.M. Gombert, C. Deutsch, Phys. Rev. A 23, 924 (1981)W. Ebeling, G.E. Norman, A.A. Valuev, I. Valuev, Contrib. Plasma Phys. 39, 61 (1999)A.V. Filinov, M. Bonitz, W. Ebeling, J. Phys. A. 36, 5957 (2003)H. Hellmann, J. Chem. Phys. 3, 61 (1935)H. Hellmann, Acta Fizicochem. USSR 1, 913 (1935)H. Hellmann, Acta Fizicochem. USSR 4, 225 (1936)H. Hellmann, W. Kassatotschkin, Acta Fizicochem. USSR 5, 23 (1936)W.A. Harrison, Pseudopotentials in the Theory of Metals (Benjamin, New York, 1966)V. Heine, M.L. Cohen, D. Weaire, Psevdopotenzcial'naya Teoriya (Mir, Moskva, 1973)V. Heine, The pseudopotential concept, edited by H. Ehrenreich, F. Seitz, D. Turnbull, Solid State Physics 24, 1 (Academic, New York 1970)G.L. Krasko, Z.A. Gurskii, JETP Lett. 9, 363 (1969)W. Ebeling, W.-D. Kraeft, D. Kremp, Theory of Bound State and Ionization Equilibrium in Plasmas and Solids (Akademie-Verlag, Berlin, 1976)W. Zimdahl, W. Ebeling, Ann. Phys. (Leipzig) 34, 9 (1977)W. Ebeling, C.-V. Meister, R. Saendig, 13 ICPIG (Berlin, 1977) 725W. Ebeling, C.V. Meister, R. Saendig, W.-D. Kraeft, Ann. Phys. 491, 321 (1979)N.N. Bogolyubov, Dynamical Theory Problems in Statistical Physics (in Russian) (GITTL, Moscow, 1946)N.N. Bogolyubov, Studies in Statistical Mechanics, Engl. Transl., edited by J. De Boer, G.E. Uhlenbeck (North-Holland, Amsterdam, 1962)H. Falkenhagen, Theorie der Elektrolyte (S. Hirzel Verlag, Leipzig, 1971), p. 369Yu.V. Arkhipov, F.B. Baimbetov, A.E. Davletov, Eur. Phys. J. D 8, 299 (2000)P. Seuferling, J. Vogel, C. Toepffer, Phys. Rev. A 40, 323 (1989)L. Szasz, Pseudopotential Theory of Atoms and Molecules (Wiley-Intersc., New York, 1985)W.H.E. Schwarz, Acta Phys. Hung. 27, 391 (1969)W.H.E. Schwarz, Theor. Chim. Acta 11, 307 (1968)N.P. Kovalenko, Yu.P. Krasnyj, U. Krey, Physics of Amorphous Metalls (Wiley-VCH, Weinheim, 2001)Z.A. Gurski, G.L. Krasko, Doklady Akademii Nauk SSSR (in Russian) 197, 810 (1971)C. Fiolhais, J.P. Perdew, S.Q. Armster, J.M. MacLaren, Phys. Rev. B 51, 14001 (1995)S.S. Dalgic, S. Dalgic, G. Tezgor, Phys. Chem. Liq. 40, 539, (2002)E.M. Apfelbaum, Phys. Chem. Liq., 48, 534 (2010)Yu.V. Arkhipov, A.E. Davletov, Phys. Lett. A 247, 339 (1998)W. Ebeling, J. Ortner, Physica Scripta T 75, 93 (1998)J. Ortner, F. Schautz, W. Ebeling, Phys. Rev. E 56, 4665 (1997)N.I. Akhieser, The classical Moment Problem (Oliver and Boyd, London, 1965)M.G. Krein, A.A. Nudel'man, The Markov Moment Problem and External Problems (American Mathematical Society, Translations, New York, 1977)M.J. Corbatón, I.M. Tkachenko, Int. Conference on Strongly Coupled Coulomb Systems (SCCS2008), Camerino, Italy, July-August, 2008, Book of Abstracts, p. 90V.M. Adamyan, A.A. Mihajlov, N.M. Sakan, V.A. Srećković, I.M. Tkachenko, J. Phys. A: Math. Theor. 42, 214005 (2009)S. Ichimaru, Statistical Plasma Physics, Vol. I: Basic Principles (Addison-Wesley, Redwood City, 1992)W. Ebeling, A. Foerster, W. Richert, H. Hess, Physics A 150, 159 (1988)H. Wagenknecht, W. Ebeling, A. Förster, Contrib. Plasma Phys. 41, 15 (2001