The Van Der Waals Forces in Gases

A calculation of van der Waal's potential of two atoms at large separation has been carried out for hydrogen and helium. The method depends upon a representation of the perturbed wave function of the system as =₀ (1+vR) where ₀ is the unperturbed wave function, v the perturbing potential and R is a function of the radial coordinates of the electrons. The method is equally well adapted to the calculation of polarizabilities. A computation of the mutual energy of two hydrogen atoms confirms the results of Eisenschitz and London. The polarizability of helium is calculated as 0. 21010^-24 cc which agrees well with the experimental value, 0. 20510^-24. The mutual energy of two helium atoms is found to be -3. 18 E₀{ (R{{a₀}) }^6}. A correlation between the mutual energy of the two molecules, , and the polarizability, , is obtained: =-1. 36{{₀}^1{2}{a₀}^3{2}a^3{2}E₀}{R^6} where ₀ is the number of electrons in the highest quantum state in the molecule, E₀ the energy of the hydrogen atom in the normal state, and R is the separation of the molecules. By means of this formula, the van der Waals cohesive pressure constant is calculated for Ne, A, N₂, H₂, O₂, and CH₄.