Method for exhaust gas after-treatment of an internal combustion engine having at least one scr catalyst

A non-transitory, computer readable storage medium containing instructions that when executed by a computer cause the computer to control an exhaust gas after-treatment of an internal combustion engine (10) having at least one SCR catalyst (22), by

• subdividing the at least one SCR catalyst (22) into at least two virtual bricks,
• controlling, by means of a first control, the at least one SCR catalyst (22) according to an overall NH3 target fill level (NH3□□□), wherein a switching from the first control into a second control for the at least one SCR catalyst (22) is performed, wherein the second control of a NH3 fill level control is performed based on a target NH3 fill level (mNH3CatSoll,SCR1B) of the first virtual brick of the at least one SCR catalyst (22).