Density-functional theory calculations improving

Figure 4.4 Trends in electrocatalysis relationships between experimentally measured specific activities for the ORR on PtsM surfaces in 0.1 M HCIO4 at 0.9 V and 333 K vs the d-band center position for (A) the Pt-skin and Pt-skeleton surfaces. Results for each alloy were collected from five independent RDE measurements and error range is expressed by the size of circles. (B) Activities and values for d-band center position predicted from (Density functional theory) calculations for (111) oriented skin surfaces. Reprinted from Science, 315,493 (2007), Vojislav R. Stamenkovic., Improved oxygen reduction activity on Pt3Ni(lll) via increased surface site availability, 493—497, 2007, with permission from Sciencemag.

Approach to Improving Approximate Exchange-Correlation Potentials Time-Dependent Density-Functional Theory Calculations of Molecular Excitation Spectra. 

There is no systematic way in which the exchange correlation functional Vxc[F] can be systematically improved in standard HF-LCAO theory, we can improve on the model by increasing the accuracy of the basis set, doing configuration interaction or MPn calculations. What we have to do in density functional theory is to start from a model for which there is an exact solution, and this model is the uniform electron gas. Parr and Yang (1989) write... 

Vibrational Spectra Many of the papers quoted below deal with the determination of vibrational spectra. The method of choice is B3-LYP density functional theory. In most cases, MP2 vibrational spectra are less accurate. In order to allow for a comparison between computed frequencies within the harmonic approximation and anharmonic experimental fundamentals, calculated frequencies should be scaled by an empirical factor. This procedure accounts for systematic errors and improves the results considerably. The easiest procedure is to scale all frequencies by the same factor, e.g., 0.963 for B3-LYP/6-31G computed frequencies [95JPC3093]. A more sophisticated but still pragmatic approach is the SQM method [83JA7073], in which the underlying force constants (in internal coordinates) are scaled by different scaling factors. 

Stratmann, R. E., Burant, J. C., Scuseria, G. E., Frisch, M. J., 1997, Improving Harmonic Frequency Calculations in Density Functional Theory , J. Chem. Phys., 106, 10175. 

Theoretical calculations and simulations using ah initio and density function theory (DFT) methodologies are also seeing increasing use. Combining these theoretical calculations with spectroscopic data can assist in the interpretation of the observed spectral features and an improved understanding of how a probe molecule interacts with the various types of sites in zeolitic systems. 

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