Page 255 - Handbook Of Multiphase Flow Assurance

254 10. Research methods in flow assurance

FIG. 10.20 Chemical structures of PVP, PVCap and VC-713.

Surfaces of sI and sII empty hydrate lattices, and hexagonal ice lattice were prepared using
SYBYL® by inputting the coordinates of the oxygen and hydrogen atoms and connecting
them into water molecules. Coordinates were generated using the Fortran program which
replicated the X-ray diffraction data for crystal unit cell in x, y and z directions. A surface of
any size and thickness could be generated. Size of the surface was made 5 × 5 × 1 sI unit cells
for sI hydrate, 4 × 4 × 1 sII unit cells for sII, and 9 × 9 × 2 repeat units for ice. The dimension of
the surface was 6.1 nm or more along x and y axes. Such sizes were chosen in order to accom-
modate the winter flounder polypeptide (5.9 nm length), 9-link chain of the VC-713 polymer
(6.1 nm length) and to reduce computation time.
The polymer chain of VC-713 and winter flounder polypeptide were generated using the
Hyperchem® release 2.0 program for Windows made by Autodesk, Inc. Potential energies of
the macromolecules were minimized in vacuo before transferring to the IBM RS-6000 work-
station. After transferring to the IBM workstation an overall energy minimization was done.