  The Moliere theory of multiple Coulomb scattering is modified to take into
account difference between scattering off atomic nuclei and electron. A simple
analytical expression for angular distribution of charged particles passing
through a thick absorber is found. It does not assume any special form for a
differential cross section and has wider range of applicability than a Gaussian
approximation. A well-known method to simulate multiple Coulomb scattering is
based on the different treatment of soft and hard collisions. An angular
deflection in a large number of soft collisions is sampled using the proposed
distribution function, a small number of hard collisions are simulated
directly. A boundary between hard and soft collisions is defined providing a
precise sampling of scattering angle (1% level) and small number of hard
collisions. A corresponding simulation module takes into account projectile and
nucleus charge distributions and exact kinematics of a projectile-electron
interaction.
