Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Van del waals interaction in qm

  1. Nov 5, 2013 #1

    I read the follow paper about van del waals interaction in quantum mechanics


    In this paper the potential

    [tex]V= e^2/R + e^2/(R+y)+e^2/(R-x)+ e^2/(R+y-x) [/tex]

    is aproximated to [tex]V \approx -2 e^2/R^3 xy[/tex]

    with R>>|x|,|y|

    why this paper use this aproximation?

    if i use Taylor series, my aproximation is

    [tex]V=4 e^2 /R + 2 e^2/R (x-y) + 2 e^2 /R^3 (x^2+y^2) -2 e^2/R^3 xy[/tex]
  2. jcsd
  3. Nov 5, 2013 #2
    ohh, sorry, my problem is with signus of V....delete my post please
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook