Abstract
The second, third, and fourth virial coefficients, Bi , of a fluid of general symmetric hard triatomic molecules (fused hard spheres) have been calculated both numerically and theoretically for a variety of potential parameters. It has been found that: (i) for B2 a valency angle ωc exists such that for ω>wc, B 2 is independent of ω, (ii) B 3 is very flat for ω>wc, and (iii) B 4 exhibits a maximum at ω∼π/2. Theoretical calculations employing an assigned convex body fit very well the second and fairly well the third virial coefficients, but fail for the fourth except in the case of a linear molecule.