Structure and Potential Surface of Liquid Methanol in Low Temperature:
A Comparison of Hydrogen Bond Network in Methanol with Water.
T. Kabeya, Y. Tamai, H. Tanaka
J. Phys. Chem., B 102, 899-905 (1998)
Abstract
Molecular dynamics simulations for liquid methanol have been carried out
in order to examine the hydrogen bond network pattern
in the low-temperature regime.
Those properties of methanol concerning hydrogen bond
connectivity are compared with supercooled water.
Methanol can be supercooled deep into the low-temperature region
without any singular behavior,
which is in sharp contrast to supercooled water.
One-dimensional linear hydrogen-bonded chains with occasional branches are
the predominant species from room temperature to 153 K.
The number of hydrogen bonds per methanol molecule
in the inherent structure
remains constant over a wide range of temperature.
Lowering the temperature simply reduces the number of branches,
keeping the total number of hydrogen bonds constant.
This is caused by a decrease of the methanol molecules
hydrogen-bonded with one and three other molecules.
It is found that hydrogen bond strength does not vary with temperature.
The potential energy of the inherent structure
decreases with a temperature decrease,
suggesting that methanol falls into a category of fragile liquid.
The energy decrease is due mainly to an increase in density
with declining temperature,
with strengthens the Lennard-Jones interaction term.
This feature is distinguished from water,
where hydrogen bonds become gradually stronger with
decreasing temperature in the normal supercooled state.
Copyright (c) 1998 Yoshinori Tamai