A molecular modelling example—adamantane

The calculation of the vibrational properties of hydrocarbons using density functional theory is usually in very good agreement with the INS experimental spectra. The treatment of the data has to take into consideration not only the contribution of the fundamentals but also the combinations and overtones. The effect of the lattice vibrations is included in an ad hoc manner ( 5.3). As an example of the usefulness of the isolated molecule approach, in Fig. 4.6 we show the experimental and calculated spectra of adamantane (tricyclo[3.3.l.l ]decane, CjoHie). 

This is an especially favourable example since the globular nature of the molecule results in only weak intermolecular interactions. Nonetheless the agreement between observation and calculation is very impressive, particularly as no scaling of the calculated frequencies was 

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