  We extend the cascade-exciton model (CEM), and the Los Alamos version of the
quark-gluon string model (LAQGSM), event generators of the Monte-Carlo
N-particle transport code version 6 (MCNP6), to describe production of
energetic light fragments (LF) heavier than 4He from various nuclear reactions
induced by particles and nuclei at energies up to about 1 TeV/nucleon. In these
models, energetic LF can be produced via Fermi break-up, preequilibrium
emission, and coalescence of cascade particles. Initially, we study several
variations of the Fermi break-up model and choose the best option for these
models. Then, we extend the modified exciton model (MEM) used by these codes to
account for a possibility of multiple emission of up to 66 types of particles
and LF (up to 28Mg) at the preequilibrium stage of reactions. Then, we expand
the coalescence model to allow coalescence of LF from nucleons emitted at the
intranuclear cascade stage of reactions and from lighter clusters, up to
fragments with mass numbers A < 8, in the case of CEM, and A < 13, in the case
of LAQGSM. Next, we modify MCNP6 to allow calculating and outputting spectra of
LF and heavier products with arbitrary mass and charge numbers. The improved
version of CEM is implemented into MCNP6. Finally, we test the improved
versions of CEM, LAQGSM, and MCNP6 on a variety of measured nuclear reactions.
The modified codes give an improved description of energetic LF from particle-
and nucleus-induced reactions; showing a good agreement with a variety of
available experimental data. They have an improved predictive power compared to
the previous versions and can be used as reliable tools in simulating
applications involving such types of reactions.
