Electronic structure algorithms

Four electronic structure algorithms have been developed, aiming at accurate and potentially useful analytic wave functions.

• Analytic atomic orbital functions
  
  Much clearer than commonly used ones, tested for the ground and excited states of several atoms, and applied for the computation of VUV photoemission of He highly excited states. (Indicatively, for the Carbon atom, 13 of our orbital functions spanning 64 configurations achieve accuracy comparable to 145 standard ''Gaussian Type Orbitals'' with 1.500.000 configurations.)
  
  
• Analytic diatomic orbital functions
  
  With similar properties as the above, applied in the computation of excited states of diatomic negative ions (a difficult task with conventional methods).
  
  
• Analytic interpolation of accurate ab initio calculations for small molecules and clusters
  
  Applied to ferromagnetic iron and other magnetic systems and successfully tested in a prototype small molecule, HCO, by fitting to a database of highly accurate ab initio calculated energy values of 500 selected HCO geometries; this algorithm results in transferable Hamiltonian matrix element (tight-binding) parameters which can be used in molecular dynamic simulations.
  
  
• Atomic VLTO Wave-function Database (04EP111 of the ENTEP-2004 programme) - {Variation Functionals for Excited States (VFES) }
  
  In graduate school courses it is taught that the variational principle can be used, by energy minimization, to compute only lowest-energy quantum states. Excited state wave functions are traditionally constructed orthogonal to lower lying approximate ones, thus, they are necessarily far from the exact. However, variational functionals, related to the energy, are presented here, for the first time, which have local minimum at exactly the nondegenerate excited quantum states of matter, allowing accurate calculations of excited state wave functionss, arbitrarily close to the exact. Via these functionals, a data-base of handy analytic and accurate wave functions is being developed for atoms and ions.
  The development of the Atomic VLTO Wave-function Database is a Deliverable of the project 04EP111 of the ENTEP-2004 programme, within Measure 8.3 of the Operational Programme "Competitiveness" of the 3rd Community Support Framework, cosponsored by 90% of the total fund by Public Funds (75% of Public Funds from the European Community - European Social Funds, 25% of Public Funds from the Greek State - Ministry of Development - General Secretariat of Research and Technology) and by 10% of the total fund by the Private Funds (the company "Virtual Trip Ltd" indirectly cosponsored the project 04EP111 as a 2nd subcontractor).
  VLTO Atomic Wavefunction Database Files & Relevantclusters Publications (.zip file 4.1 MB)
  
  
• Cluster heterogeneous Catalysis
  
  Small metal clusters of otherwise catalytically inactive bulk metals, may develop heterogeneous catalytic properties due to geometrical anomalies comparable to the active center site of the reactants. The interaction of small Aluminum with CH₄ or with O₂ is being investigated.

TPCI Staff
Researchers: N.C. Bacalis
Graduate Students: E.I. Alexandrou

Collaborations
AMS Research Center, Southeast University, Nanjing, China, Dr. Z. Xiong,
Chemistry Department, Ulm University, Germany, Prof. Dr. Axel Gross
Department of Physics, Aristotle University of Thessaloniki, Greece, Dr. H. Polatoglou.
Department of Physics, University of Ioaninna, Greece, Dr. N.I. Papanicolaou
Hellenic Petroleum S.A., Greece, Dr. M. Darthas
Private collaborator: Dr. Aristophanes Metropoulos.
Private collaborator: Dr. D. Karaoulanis.

Support
GSRT Grants No. 03EΔ968 and No. 04EP111

Contact
N.C. Bacalis
Theoretical and Physical Chemistry Institute,
National Hellenic Research Foundation,
48 Vassileos Constantinou Ave.,
Athens 11635, Greece

Tel.: +30 210 7273802
FAX: +30 210 7273794
Email: nbacalis