Density Functional Theory (DFT) calculations have been extensively used as a powerful tool for predicting several molecular properties, such as geometry, vibrational frequencies, and their infrared and Raman intensities during the last decade. Understanding the efficiency and accuracy of these methods in predicting the molecular properties could be very useful for theoretical and practical chemists. Knowledge about the efficiency and accuracy of these methods saves valuable time when selecting the most effective and economic method. Acetone, acetaldehyde, and ethyl-methyl ketone were selected because of the extensive experimental works on their vibrational frequency, and IR intensity.

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