# Concentration¶

## Reading of initial concentration from file¶

Using the flag from_file, MICRESS is able to read the initial concentration fields either from an ASCII profile or from a 2-D or 3-D ASCII array file.

The easiest way of creating an ASCII input file is writing ASCII outputs for single time steps with DP_MICRESS. Such a file can afterwards serve as a template for the real data. For each ASCII file the dimensions (CellsX, CellsZ: number of grid points in x and z direction) have to be given, the compositions are interpolated to the actual dimension of the simulation domain. If necessary, the data can be flipped or transposed. If a thermodynamic database is used, a composition for initialisation of the thermodynamic description has to be given additionally. From these data, an initial equilibrium is calculated, and the corresponding thermodynamic description is stored for all the interface regions. These data will be used until a relinearization is performed.