Atomic simulations of the dislocation core show that the atomic misfit
is often concentrated in the glide plane. Instead of using a step fun
ction to describe the displacement as in a classical Volterra dislocat
ion, a better description is obtained by a Peierls dislocation for whi
ch the displacement is assumed to have an arctg like shape. The slope
in the center is determined by requiring that the total energy must be
a minimum. The elastic energy can be expressed in closed form, and wi
th the availability of high speed computing the atomic misfit energy i
n the glide plane can be calculated by standard numerical integration
without any difficulties. When the Peierls model is extended to two di
mensions the resulting line energy, line tension and resistance agains
t bow-outs of straight dislocations can be obtained realistically with
out any adjustable parameters and the way that these quantities are in
fluenced by the interplanar atomic potential can be studied. In additi
on to undergoing the well-known ''dissociation'', a mixed dislocation
may lower its energy by a ''deviation'' in which the displacement vect
or deviates from the direction of the crystallographic Burgers vector
even when this runs along a path of lowest misfit energy. (C) 1997 Act
a Metallurgica Inc.