Journal of Statistical Physics, Vol. 45, Nos. 1/2, 1986. p. 171-181.
New expressions for the elastic moduli of a classical system are derived. They involve only the two-point correlation function and the derivative of the one-point correlation function, both only on the boundary of the system. These expressions, valid for any interaction derivable from a potential, are proved from a mechanical point of view by generalizing the virial theorem of Clausius, and from a statistical point of view by a direct method that constitutes an alternative to Green's dilatation method.