Assessing the reliability of calculated catalytic ammonia synthesis rates

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Science  11 Jul 2014:
Vol. 345, Issue 6193, pp. 197-200
DOI: 10.1126/science.1253486

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Assessing calculated DFT properties

Density functional theory (DFT) is now widely used to calculate molecular and material properties. DFT's reliability is usually assessed by comparison with experimental values and higher-level theoretical methods. Medford et al. used the BEEFvdW, an exchange-correlation density functional tailored for surface chemistry, and looked at uncertainties with ensembles of functionals. For the specific case of ammonia synthesis catalyzed by transition-metal surfaces, relative rates between different catalysts had lower errors than the absolute rates.

Science, this issue p. 197


We introduce a general method for estimating the uncertainty in calculated materials properties based on density functional theory calculations. We illustrate the approach for a calculation of the catalytic rate of ammonia synthesis over a range of transition-metal catalysts. The correlation between errors in density functional theory calculations is shown to play an important role in reducing the predicted error on calculated rates. Uncertainties depend strongly on reaction conditions and catalyst material, and the relative rates between different catalysts are considerably better described than the absolute rates. We introduce an approach for incorporating uncertainty when searching for improved catalysts by evaluating the probability that a given catalyst is better than a known standard.

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