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tokens: fraction, χ i , of the gas that inflows from the i + 1th annular ring to the i th ring during the simulation time-step of 1 Myr. If we assume that the entire interstellar gas fraction within an annular ring participates in the radial inflow, the percentage area of the annular rings involved in the radial mass inflow across a ring during 1 Myr with the chosen radial inflow velocities of 0, 0, 0.5, 1, 2, 3, and 3.7 km s −1 would be 0, 0, 0.02, 0.05, 0.09, 0.14, and 0.17 per cent, respectively, from the first to the seventh ring. This corresponds to a substantial inflow of gas causing a strong depletion of gas as well as the total surface matter density in the outer annular rings at the cost of matter accumulation in the inner rings. In order to circumvent this excessive inflow of gas towards the centre, we assumed 0.1 mass fraction of the total available gas fraction to be actively involved in the inflow. Thus, we used the values of 0, 0, 0.002, 0.005, 0.009, 0.014, and 0.017 per cent for χ i , from the first to the seventh ring. The assumed radial profiles of the halo surface mass density in Models I and J are presented in Table 1 . The radial stellar formation efficiency parameter, , in these simulations is assumed to be unity over the entire Galaxy. As discussed later in Section 4 , the radial gas inflow provides a natural mechanism to obtain the observed elemental abundance gradients without adopting a preferred set of stellar efficiency parameters. Finally, the choice of the simulation parameters made in this work is certainly not restricted (Mott et al. 2013 ). We have also simulated a Model J in order to incorporate the radial gas inflow superimposed over the radial gas mixing. The mixing was performed in a manner identical to that of Model F with a mixing velocity of 1 km s −1 . We have not specifically performed the simulation with radial gas outflows that are mainly caused by the energetic winds from supernovae and other massive stars. The radial gas mixing models take care of this aspect to an extent. 3 RESULTS The major aim of this work was to develop a Monte Carlo based GCE model for the Milky Way Galaxy. We ran a large number of simulations to optimize the various simulation parameters based upon the observational constraints. A selective set of simulation results for our three best models A, H, and J are presented in Figs 1 – 10 and Table 1 . We have avoided a detailed discussion and presentation of the simulation results for Models B–G and I in the main text. The results of these models can be found in figs 11–31 in the supplementary data . However, we summarize the major findings of these models in the main text. We present a comprehensive account of the deduced evolution of the , the [Fe/H], the metallicity , and the stellar birth rate for the various annular rings of 2 kpc width each, starting from 2 to 18 kpc from the Galactic centre. The deduced temporal evolution of the total surface mass density (stars +