Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...

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where a = a0(Z1 2/3 + Z2 2/3 ) -½ and is the Thomas-Fermi screening function which is
tabulated numerically. An approximation to the function is also given by,
r
r
a
(3.9)
2 1
a r 2 2 [ c ]
a
with c 3 resulting in the best average fit to the potential.
Using approximation methods in finding the solution the LSS theory predicts a
nuclear stopping power Sn of the form shown in Fig. 3.1.
Fig. 3.1. Nuclear and electronic stopping powers in reduced units. Full-drawn curve
represents the Thomas-Fermi nuclear stopping power, the dot and dash lines the
electronic stopping for k=0.15 and k=1.5. The dashed line gives the nuclear stopping
power for the r -2 potential (from Carter et al. (1976))
The energies and distances are expressed in terms of dimensionless parameters ε and
ρ given by,
aM 2
E
(3.10)
2
Z Z e M M )
1
2
( 1 2
M M
RN4a
(3.11)
2 1 2
and 2
( M 1 M 2 )