An ab initio molecular orbital study of the argon hydride molecule–ions, ArH+ and ArD+, at the MP4(SDQ)/6-311++G(3df,3dp) level. III: a study of some physical properties of ArH+, compared with those of HeH+, NeH+ and KrH+ and the diatomic Van der Waals mo

This Letter reports some calculated MO MP4/6-311++G(3df,3dp) physical properties of ArH+, such as the variation of the Mulliken charge density with internuclear distance R. These values are compared with those calculated for HeH+, NeH+ and KrH+. In addition, the Born–Oppenheimer (BO) potential energies (PE) of the molecules He2, Ne2, Ar2 and Kr2 are explored and compared with the Lennard-Jones (LJ) potentials from theory and experiment. The LJ constants ε and σ and the second virial coefficients B(T) of the noble gases, calculated from the BO and LJ potentials, are then used to explore some suggested trends in the physical properties of ArH+. Some problems experienced with the calculations on NeH+ and Ne2 are also reported.