Virial theorem constraints on n-body terms of potential energy surfaces

The virial theorem for the n -body energy terms in a cluster expansion of potential energy surfaces has been investigated. Integral conditions on the uniform scaling cuts of the kinetic and potential components of the n -body energy term are reported. The corresponding relations for n -body energy terms of molecular fragments are also examined. A use of the integral relations as constraints on the model n -body functions is suggested. An example is presented for the ground state surface of Li 3 .