We introduce a simple procedure for generating spectral line shifts in diatomic fluids as a function of pressure. From O(100) configurations (of 100 N-2 molecules) sampled in an isothermal-isobaric ensemble, forces computed with density functional theory are used to generate force-displacement correlations at a series of fluid densities. The curves are fitted with second-degree polynomials, and the resulting coefficients are related to fundamental frequencies and anharmonicities through a truncated expansion of the Morse potential. Comparison to coherent anti-Stokes Raman data reveals satisfactory agreement for line shifts as a function of pressure. (C) 2008 Elsevier B.V. All rights reserved.