Wavefunctions and Correlation Energies for Two-, Three-, and Four-Electron Atoms

any estimate of !.1 is attempted. It will be noted that the values from virial coefficients (±6, ±5) are appreciably larger than our value and may reflect the fact that in selecting parameters for the 12-6 core potential, the dispersion forces were underestimated leading to a corresponding overestimate of the effect of an octopole moment. An evaluation of the quantum-mechanical estimates of !.1 is still more difficult. For the most part they lie below estimates from virial coefficients, although three values are higher.6•7 The most recent value available to us represents the lowest value yet obtained by calculation.8 If one were to use our value of !.1 to judge the wavefunctions employed in the calculations, then the wavefunctions of Sinai9 and of Albasiny and Cooper7 would appear to be the most appropriate. Our value for the octopole moment of carbon tetrafluoride is ± 13. 7X 1o-34 esu • cm3, somewhat larger than the value of 4.4X 1oesu · cm estimated by Parsonage and Scott from phase transition data.2 6 A. G. Turner, A. F. Saturno, P. Hauk, and R. G. Parr, J. Chern. Phys. 40, 1919 (1964); W. T. King, ibid. 39, 2141 (1963). 7 E. L. Albasiny and J. R. A. Cooper, Proc. Phys. Soc. (London) 82, 289 (1963). 8 R. M. Pitzer (private communication). 9 J. J. Sinai, J. Chern. Phys. 40, 3596 (1964); 39, 1575 (1963).