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The temperature dependent structure of liquid 1-propanol as studied by neutron diffraction and EPSR simulations

Per Sillrén (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Jan Swenson (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Johan Mattsson ; Daniel Bowron ; Aleksandar Matic (Institutionen för teknisk fysik, Kondenserade materiens fysik)
Journal of Chemical Physics (0021-9606). Vol. 138 (2013), 21, p. 214501.
[Artikel, refereegranskad vetenskaplig]

The structure of liquid 1-propanol is investigated as a function of temperature using neutron diffrac- tion together with Empirical Potential Structure Refinement modelling. The combined diffraction and computer modelling analysis demonstrates that propanol molecules form hydrogen bonded clusters with a relatively wide size distribution, which broadens at lower temperatures. We find that the clus- ter size distribution is well described by a recently proposed statistical model for branched H-bonded networks [P. Sillrén, J. Bielecki, J. Mattsson, L. Börjesson, and A. Matic, J. Chem. Phys. 136, 094514 (2012)]. The average cluster size increases from ∼3 to 7 molecules, whilst the standard deviation of the size distribution increases from 3.3 to 8.5 as the temperature is decreased from 293 to 155 K. The clusters are slightly branched, with a higher degree of branching towards lower temperatures. An analysis of the cluster gyration tensor (Rmn) reveals an average elongated ellipsoidal shape with axes having proportions 1:1.4:1.9. We find that the average radius of gyration has a cluster size dependence consistent with that of fractal clusters, Rg ∝ n1/D , with a fractal dimension D ≈ 2.20, which is close to D = 2.00 expected for an ideal random walk or D = 2.11 expected for reaction limited aggregation. The characteristic angles between the H-bonded OH-groups that constitute the clusters show only a weak temperature dependence with O–H· · ·O angles becoming more narrowly distributed around 180◦ at lower temperatures.

Nyckelord: Neutron Diffraction, propanol, hydrogen bonding

Denna post skapades 2013-07-13. Senast ändrad 2015-12-17.
CPL Pubid: 180137


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Institutionen för teknisk fysik, Kondenserade materiens fysik (1900-2015)



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