Physics & Astronomy ETDs

Publication Date



The theoretical study of dense gases with strong intermolecular forces is impeded by lack of sufficient experimental which to compare predictions of the properties. High speed computers can supply this information by calculating the detailed dynamics of molecular assemblages, thereby taking the place of an actual physical experiment. This information supplied by the computers not only can test the validity of existing theories, but also it can indicate directions for possible im­provement in the theoretical approximations.

In order to show the adaptability of computers to this task, this thesis deals with the theoretical and computer-experimental study of the force exerted an end wall. The gas particles were restricted to move in one space dimension and to have only nearest neighbor interactions.

The theoretical approach predicted a force on the wall by using an approxi­mate solution to the time independent Liouville equation. The experimen­tal data were obtained from the computer, which was programmed to simulate in detail the dynamics of the particles. Finite-difference approxima­tions were written for the Newtonian equations of motion and were solved algebraically by the computer.

This thesis presents comparisons for one-dimensional gas systems under a variety of conditions: different interparticle forces, two types of wall boundaries, several average energies per particle, and various numbers of particles in the system. The interparticle force was either inversely proportional to the separation distance between particles or repulsive, or else of Lennard-Jones type, with both repulsive and attractive terms. Most comparisons were made with the simpler repulsive force function. The boundaries were either specular or fixed-particle. In the latter, a particle identical with all others in the system remains stationary and forms a wall. Theory agreed well with the computer experiments for the repulsive force function. For the Lennard-Jones type, agree­ment ranged from good to poor.

Finally, a discussion is presented which shows the possibility of applying this technique to more physically realistic problems in two space dimensions.

Degree Name


Level of Degree


Department Name

Physics & Astronomy

First Committee Member (Chair)

Christopher Pratt Leavitt

Second Committee Member

Francis H. Harlow

Third Committee Member




Document Type