  We present geometrical and physical optics simulation results for the Simons
Observatory Large Aperture Telescope. This work was developed as part of the
general design process for the telescope; allowing us to evaluate the impact of
various design choices on performance metrics and potential systematic effects.
The primary goal of the simulations was to evaluate the final design of the
reflectors and the cold optics which are now being built. We describe
non-sequential ray tracing used to inform the design of the cold optics,
including absorbers internal to each optics tube. We discuss ray tracing
simulations of the telescope structure that allow us to determine geometries
that minimize detector loading and mitigate spurious near-field effects that
have not been resolved by the internal baffling. We also describe physical
optics simulations, performed over a range of frequencies and field locations,
that produce estimates of monochromatic far field beam patterns which in turn
are used to gauge general optical performance. Finally, we describe simulations
that shed light on beam sidelobes from panel gap diffraction.
