CCP9 - Computational Electronic Structure of Condensed Matter

Beyond LSD

Introduction

The aim of this project is to obtain an improved density functional theory for those systems where the local density approximation (LSD) is known to fail. The systems are the highly correlated compounds such as transition metal oxides (including the parent compounds to the high Tc materials and CMR compounds) and rare earths which also encompasses the heavy fermion systems. The method implemented is the self-interaction-corrected (SIC) local spin density. This approach is physically transparent as it describes the localised states of the system with a potential which has the spurious (and non-negligible) self-interaction subtracted, whilst the band-like states remain solutions of the LSD potential.

Scientific Highlights

  1. The relativistic generalization SIC was developed and applied to a study of the orbital properties of γ-Ce. This work was published as a Physical Review Letter in 1997 and involved CCP9's Sheffield-Daresbury collaboration.
  2. The SIC-LSD for NiO was compared with the semi-phenomelogical LDA+U approach in a collaboration involving Oxford and Daresbury.
  3. The valencies of all the rare-earths and rare-earth sulphides were calculated from first principles. This has given new insight into the formation of the divalent state in some of the rare earths. This work was published in Nature and involved CCP9's collaboration between Keele and Daresbury.
  4. The ab initio approach to the calculation of the valency of Yb in compounds, where Yb can occur in a divalent, trivalent or intermediate valence state, was compared with a semi-phenomelogical approach due to B. Johansson (Uppsala University). This gave new understanding in the electronic properties of several Yb compounds. This work involved the Keele-Daresbury group and was published in Physical Review Letters.
  5. Divalent and trivalent Cu in YBCO were studied. In YBa2Cu3O6, the Cu in the CuO2 planes is found to be divalent and insulating. In YBa2Cu3O7, however, these Cu ions became trivalent with a near degeneracy with the divalent state. This work was submitted for publication to Physical Review Letters.

Future Work

Funding is requested for collaborative visits and mini-workshops to perform the following:

  1. Determine the applicability of the SIC-LSD for the study of the manganites (CMR compounds). This involves the Sheffield-Daresbury collaboration.
  2. Further studies of the electronic properties of rare earth compounds by the Keele-Daresbury collaboration.
  3. Determine the applicability of the SIC-LSD for the study of ruthenates and other 4d transition metal oxides.
  4. Optimization of the relativistic SIC-LSD code so that a systematic study of the orbital properties in transition metal oxides, rare earths and actinides can be performed.
  5. Incorporation of virtual crystal type of approximation in the SIC-LSD code to treat nonstochiometry in the weak scattering sub-lattices
  6. Incorporation of dichroism codes into the SIC-LSD code. This specifically to support the experiments on oxides and f-systems on the Synchrotron in Daresbury.
  7. Study the feasibility of the development a local SIC-LSD formalism. This would allow a Green's function formulation of the SIC and open up new applications such as surfaces, interfaces and alloys. This involves a Bristol-Daresbury collaboration.
  8. Study of the Fermi surface of YBa2Cu3O7-x in the underdoped regime.

Publications 1997-1999

  1. A. Svane, Z. Szotek, W. M. Temmerman and H. Winter,
    "Theory of the Electronic and Magnetic Structure of Cerium Pnictides under Pressure",
    Solid State Communications 102 (1997) 473-477.
  2. S.V. Beiden, W.M. Temmerman, Z. Szotek and G.A. Gehring,
    "Self-Interaction Free Relativistic Local Spin Density Approximation: Equivalent of Hund's Rules in γ-Ce",
    Phys. Rev. Lett. 79 (1997) 3970-3973
  3. W. M. Temmerman, Z. Szotek, A. Svane, H. Winter, S.V. Beiden and G.A. Gehring,
    "Applications of Self-Interaction Correction to Localised States in Solids",
    HPC Profile, The National Publication for High Performance Computing Applications and Techniques, Eds. R. J. Allen and M. F. Guest, 17 (1997) 5-7
  4. S.L. Dudarev, G.A. Botton, S.Y. Savrasov, Z. Szotek, W.M. Temmerman and A.P. Sutton,
    "Electronic structure and elastic properties of strongly correlated metal oxides from first principles: LSDA+U, SIC-LSDA and EELS study of UO2 and NiO",
    phys. scat. sol. (a) 166 (1998) 429
  5. A. Svane, Z. Szotek, W. M. Temmerman, J. Laegsgaard and H. Winter,
    "Electronic Structure of Cerium Pnictides under Pressure",
    J. Phys.: Condens. Matter 10 (1998) 5309-5325
  6. W.M. Temmerman, Z. Szotek, A.C. Jenkins, A. Svane, H. Winter, S.V. Beiden and G.A. Gehring,
    "An Unified Bandstructure Description of Localized and Delocalized F States",
    in Magnetism and Electronic Correlations in Local Moment Systems: Rare Earth Elements and Compounds, eds. M. Donath, P.A. Dowben & W. Nolting, World Scientific Publishing Co. ISBN 981-02-3538-0 (1998) 21-33
  7. W.M. Temmerman, A.Svane, Z. Szotek and H. Winter,
    "Applications of Self-Interaction Corrections to Localized States in Solids",
    in "Electronic Density Functional Theory: Recent Progress and New Directions" Eds J. F. Dobson, G. Vignale and M. P. Das, Plenum, NY (1998) ISBN 0-306-45834-9
  8. A. Svane, W. M. Temmerman and Z. Szotek,
    "Theory Of Pressure Induced Phase Transitions in Cerium Chalcogenides",
    Phys. Rev. B 59 (1999) 7888-7892
  9. P. Strange, A. Svane, W.M. Temmerman, Z. Szotek and H. Winter,
    "Ab-initio description of the valency of rare earths",
    Nature 399 (1999) 756-758
  10. Z. Szotek, W.M. Temmerman, A.Svane, H. Winter, S.V. Beiden, G.A. Gehring, S.L. Dudarev and A.P. Sutton,
    "Applications of Self-Interaction Corrections to Localized States in Solids",
    in High-Performance Computing, Eds. R.J. Allan, M.F. Guest, A.D. Simpson, D.S. Henty and D.A. Nicole, Kluwer Academic/ Plenum Publishers, ISBN 0-306-46034-3 (1999) 207-212
  11. A. Svane, W. M. Temmerman, Z. Szotek, J. Laegsgaard and H. Winter
    "Self-Interaction Corrected Local-Spin-Density Calculations for Rare Earth Materials",
    accepted for publication to Int. Journal Quantum Chemistry (1999)
  12. W.M. Temmerman, Z. Szotek, A. Svane, P. Strange, H. Winter, A. Delin, B. Johansson, O. Eriksson, L. Fast and J.M. Wills,
    "Electronic Configuration of Yb Compounds", Phys. Rev. Lett. 83 3900 (1999)
  13. W.M. Temmerman, A.Svane, Z. Szotek, H. Winter and S. Beiden,
    "On the implementation of the Self-Interaction Corrected Local Spin Density Approximation for d- and f-electron systems",
    Lecture Notes in Physics, Springer-Verlag (1999), to be published
  14. W.M. Temmerman, Z. Szotek, H. Winter and A. Svane,
    "Energetics of Divalent and Trivalent Cu in YBCO",
    submitted to Phys. Rev. Lett. (1999)