MOLECULAR-DYNAMICS SIMULATION OF BIPHENYL DISSOLVED IN A LIQUID-CRYSTALLINE SOLVENT - A TEST OF THEORETICAL METHODS OF DERIVING ROTATIONAL POTENTIALS FROM PARTIALLY AVERAGED NUCLEAR-SPIN DIPOLAR COUPLINGS
We. Palke et al., MOLECULAR-DYNAMICS SIMULATION OF BIPHENYL DISSOLVED IN A LIQUID-CRYSTALLINE SOLVENT - A TEST OF THEORETICAL METHODS OF DERIVING ROTATIONAL POTENTIALS FROM PARTIALLY AVERAGED NUCLEAR-SPIN DIPOLAR COUPLINGS, The Journal of chemical physics, 105(16), 1996, pp. 7026-7033
A molecular dynamics simulation has been carried out of biphenyl disso
lved in a solvent comprised of rigid particles interacting with the Ga
y-Berne potential, The solution is investigated in isotropic, nematic,
and smectic phases, and the probability distribution, P-LC(phi) obtai
ned, where phi is the angle between the two ring normals. This is comp
ared with P-mol(phi), the distribution calculated for an isolated mole
cule, and it is found that the positions, phi(max) of the maxima of th
e two distributions differ by about 2 degrees, The molecular dynamics
trajectory is used to calculate averaged nuclear spin dipolar coupling
s, D-ij, and these are used to test the maximum entropy (ME) and addit
ive potential (AP) theoretical models which have been used previously
to obtain the distribution P-LC(phi) from dipolar couplings obtained o
n real solutions of biphenyl in liquid crystalline solvents. It is con
cluded that the AP method is able to recover the true distribution PLC
(St) from the simulated D-ij with good precision at all the temperatur
es studied, whereas the ME method achieves good precision only when th
e orientational order is high. The AP method also succeeds in obtainin
g the correct difference between P-LC(phi) and P-iso(phi), the distrib
ution for an isotropic phase at the same temperature. (C) 1996 America
n Institute of Physics.