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Unformatted text preview: Computer project 3 PHZ 5156 Results due Tuesday, October 21 In this project, we will write and use a simple molecular dynamics code to simulation noble gas atoms interacting via a LennardJones potential U ( r ) = 4 r 12 r 6 It is typical to ignore interactions beyond some cutoff, which we can reasonably choose to be r cut = 3 . (see Fig. 9.1 in Giordano). This speeds up the calculation quite substantially especially as we go to larger and larger systems. However, we then have the issue of a discontinuous potential and also discontinuous derivatives (Giordano doesnt really explore these issues). The potential can be slightly altered so that U ( r ) and its derivative are continuous at r = r cut . We can use, U ( r ) = 4 r 12 r 6 4 " r cut 12 r cut 6 # + 24 r cut " 2 r cut 12 r cut 6 # ( r r cut ) for r r cut . For r > r cut , the potential and forces are all zero. Verify that this potential and the forces are continuous at r = r cut . Note that there are a lot of constant terms that we can calculate once at the beginning of the program to make...
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 Fall '08
 Johnson,M

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