OVGF method

For what types of electronic states the use of TD-DFT and OVGF methods to compute excitation energies is appropriate and when these methods are not expected to provide accurate results ... 

The combination of P3 or OVGF methods with the QVOS approximation procedure ranks as follows with respect to accuracy when a 50% reduction of the virtual orbital space is performed ... 

Comparison of this conclusion with the ordering given in the introduction indicates that there are now many more options for the calculation of EADEs with quasiparticle electron propagator methods. Furthermore, the accuracy gap between EP2 and P3 or OVGF methods has been filled and better compromises for accuracy and computer resources are available for large molecules. In particular, the QVOS... 

CPH(327)269>, calculated by OVGF method and the 6-311 -I-I-G basis set. " <2006CPH(327)269>, calculated by HF method and the aug-cc-pVTZ basis set. <2006CPH(327)269>, calculated by DFT/B3LYP method and the aug-cc-pVTZ basis set. 

Hu is the first ionized state of the C60. An IE value of 7.67 eV is obtained with the OVGF method. The PS of 0.89 indicates a one-electron process. The ADC(3) method gives 7.68 eV with a PS value of 0.87, thus confirming the one-electron nature of this ionization. Both methods are in excellent agreement with the experimental value [37]. 

A reliable electronic-structure model which provides a balanced description of the electronic states of interest is required for the computation of inter-state vibronic coupling constants. In particular, artifactual symmetrybreaking effects in the electronic wave function should be avoided. For excited electronic states, a CASSCF/MRCI description with appropriately chosen active space is generally to be recommended. For ionized states, the OVGF method, the ADC(3) method or the EOM-CC method have been found to be appropriate tools. 

Application of OVGF Method for Calculations of Ionization Potentials of Molecules... 

It was shown previously in a series of papers " that the OVGF method, developed by the Cederbaum group,can be coupled to NDDO-based semiempirical molecular orbital... 

The theory of the OVGF method and the explicit formulas are given in Ref. 4. Here we briefly present some of the main features of this method, and the interested reader is referred to Ref. 4 for more theoretical details. 

In many cases we are not interested in the full ionization spectrum, but only in the first few IPs for the outer valence electrons. The method which takes into account only the outer valence region is known as the OVGF method. It was shown by Cederbaum et al." that in the OVGF method G(IP) can be used in a diagonal form. Diagonal approximations in the self-energy matrix in the ab initio framework have proven successful for outer valence lEs and EAs of closed shell molecules. By taking this into account, equation (9) can be rewritten as... 

We have extended the application of the OVGF method to the calculation of IPs of radicals as well. The SCF orbital energies were calculated by the half-electron (HE) method, using doublet correction for IPs. The SAMI, AMI. and OVGF(AMl) calculated vertical IPs of 28 organic radicals (see Scheme 3) are collected in Table 7 together with available experimental data. 

A comparison of the computed IPs of the radicals shows that the OVGF method generally gives lower lEs than the values calculated by using KT and for some of th radicals the lowering is about 0 5 eV. The mean deviation A for the OVGF(AMl) method is only ca. 0.33 eV and it becomes even less (0.29 eV) if we exclude the result for the trifluoromethyl radical, which deviates from the experimental value by more... 

We have used the outer valence Green s function (OVGF) method coupled with semiempirical approximations to calculate the IPs of a variety of molecules ranging from benzene to fullerenes. We also extended the method to calculate IPs... 

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