Search results for "Short range order"

Structural features of selected protic ionic liquids based on a super-strong base

2019

Protic ionic liquids (PIL) were prepared from a super-strong base 1,7-diazabicyclo[5.4.0]undec-7-ene (DBU) and super-strong acids, trifluoromethane sulfonic acid (TfOH), and (trifluoromethanesulfonyl)-(nonafluorobutylsulfonyl)imide, (IM14H), ([DBUH][TfO] and [DBUH][IM14], respectively; the latter for the first time) and their chemical and physical properties and structural features have been explored using a synergy of experimental and computational tools. The short range order in neat DBU, as well as the long range structural correlations induced by charge correlation and hydrogen bonding interactions in the ionic liquids, have been explored under ambient conditions, where these compounds …

1992

The molecular packing and spatial correlations of polymers [CH 2 CR(COOR')] n (R= H, Me; R'= (CH 2 ) 11 + NMe 2 (CH 2 ) 3 SO 3 - ; (CH 2 ) 2 + N(Me)[(CH 2 ) 3 SO 3 - ][C 10 H 21 ]) are studied by means of X-ray analysis and conformational calculations. The analysis of the correlation functions and density distribution profiles suggest a double-layered molecular packing which is discussed for the three polymers investigated, with respect to their different chemical structures. Whereas the zwitterionic polymethacrylates studied exhibit liquid-like short-range order, the polyacrylate analog exhibits an ordered double-layered superstructure

Molecular Dynamics Study of Disordering and Premelting of the Pb(110) Surface

1994

Molecular dynamics simulations incorporating a many-body (glue) potential have been used to investigate the atomic structure and dynamics of the Pb(110) surface in the range from room temperature up to the bulk melting point. The Pb (110) surface starts to disorder approximately at 360 K via the generation of vacancies and the formation of an adlayer. At about 520 K we observe the onset of a quasiliquid region at the surface, which exhibits liquid-like energetic, structural and surface properties. The disordering is enhanced in the direction parallel to the close-packed rows. While losing long range order, the two outermost quasiliquid layers retain a considerable degree of short range orde…

Raman spectrum of the high pressure phase of polyethylene

1982

The Raman spectrum of the hexagonal high pressure phase of polyethylene was measured at 5.2 kbar and 240 °C, using a hydrostatic high pressure cell. The spectrum is largely identical to that obtained for the melt. This result indicates that the conformational short range order in the hexagonal phase remains melt —like and is not modified by the overall straightening of chains.

Local Environment of Co2+ Ions in β″-Alumina Crystals

1992