Alkanes, Phase Changes and Bob

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Alkanes, Phase Changes and Bob
H. L. Strauss, D. Clavell-Grunbaum, R.G.
Snyder Chemistry, UC Berkeley 1)Bob Snyder
Master of Alkane (Methylene) Spectra 2)Assignments
in Detail, leading to understanding of phases,
order and disorder 3)Kinetics of phase changes.
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Title VIBRATIONAL ANALYSIS OF THE N-PARAFFINS
.2. NORMAL CO-ORDINATE CALCULATIONS Author(s)
SCHACHTSCHNEIDER JH, SNYDER RG Source
SPECTROCHIMICA ACTA 19,117(1963) Cited 1,110
UNSTABLE SOLID-STATE BINARY n-ALKANE MIXTURES
STRUCTURE AND MEASUREMENT OF TIME EVOLUTION OF
THE CONCENTRATION DISTRIBUTION R.G. Snyder, D.
Clavell-Grunbaum, and H. L. Strauss JPC B 111,
13957 (2007)
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Phases, Mixture
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W.C. Carter, MIT
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http//www.lnsm.eu/related-topics/
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Reference Mitures Values of xAi for C30H and
C30D in Base-Set (no separation) i C30H
C30D 1 0 0 2 0.055 0.056 3 0.102
0.114 4 0.216 0.195 5 0.307 0.298 6 0.398
0.387 7 0.503 0.497 8 0.613 0.602 9 0.702
0.693 10 0.805 0.784 11 0.886 0.898 12 0.944
0.945 13 1.000 1.000
Note the i 1 mixture for C30H is the i 13
mixture for C30D, etc.
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Mole Fraction (local fraction) vs Time
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R(t), measure of the extent 0f Phase Separation

• Average concentration squared normalized by
  initial concentration
• Start at conc of A of 1/3 (mole fraction). R(0)
  equals (1/3) squared times a mole fraction of 1
  over 1/3 to give 1/3.
• R(?) equals (1) squared times a mole fraction of
  1/3 (plus 0 times 2/3) over 1/3 to give 1.

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R(t), the sum of local concentrations squared vs.
log time
Normalized, so that values start at the
concentration and tend to 1
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Conclusions

• Model for spinodal phase separation
• X-ray and Neutron diffraction measure long range
  order
• Our method determines short range order (molecule
  and its immediate neighbors)
• Results consistent with theories of spinodal
  separation.
• Need computer simulations