The background simulation of experiment for searching of $2 u2K$ capture in Xe-124

We describe the Monte Carlo (MC) simulation package of the `2K-CAPTURE setup and discuss the agreement of its output with data. The `2K-CAPTURE MC simulates the energy loss of particles in detector and components of the passive shield and generates the resulting response in working volume large proportional counter (LPC). The simulation accounts for absorption, reemission, and scattering of both photons and neutrons and tracks them until they either are absorbed. The algorithm proceeds with a detailed simulation of the electronics chain. The MC is tuned using data collected with radioactive calibration source deployed in the internal channel of the installation. The simulation reproduces the energy response of the detector corresponding to distribution of the generated pointwise clusters of a charge of primary ionization in LPC.