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The isomers of small molecule alcohols propanol (PrOH) and butanol (BuOH) are studied by x-ray Compton scattering experiments with synchrotron radiation and density-functional theory calculations. The lineshape of the measured spectra, i.e., the Compton profile, is a momentum-space property, and its changes reflect changes in the electronic charge density between the isomers. Compared to the linear alcohols (n-PrOH and n-BuOH), the Compton profiles of the branched alcohols (iso-PrOH, iso-BuOH, sec-BuOH) are found to be narrower, which indicates a more delocalized charge for the latter. The calculations are performed for systems consisting of one to three monomer units and are found to reproduce reasonably the experimental spectral features. The influence of the basis set and exchange-correlation scheme is studied in more detail. The results provide new insight into the isomeric differences in small molecule alcohols and show that quantum chemical calculations can be increasingly tested against the x-ray Compton scattering data. [ABSTRACT FROM AUTHOR]

The electronic structure of elemental silicon has been studied under high pressure using high-energy Compton scattering utilizing synchrotron radiation. The experiment was realized using a special Laue monochromator and a novel assembly of compound refractive lenses. The extremely good focusing enabled us to utilize a Mao–Bell version of the Merrill–Basset diamond anvil cell with a Be gasket up to a pressure of 20 GPa. After the careful subtraction of background scattering, the Compton profile difference for the metastable Si-XII to the Si-V phase was extracted and compared with the theory. The results clearly demonstrate the feasibility and potential of the Compton scattering technique as a complementary tool in the study of electronic structure of materials under high pressure. [ABSTRACT FROM AUTHOR]