im currently trying to implement the ZLB into the “model of unconventional monetary policy” by Mark Gertler and Peter Karadi in a deterministic setting using the code of the Macroeconomic Model Database. As usual I am using the max operator on the Taylor Rule in order to do that. But as soon as the model hits the ZLB I always get the problem that the perfect foresight solution is no longer found and although the results look the way they should, there is the problem that the real rate jumps at the beginning. I also tried the perfect foresight model with a Levenberg-Marquardt mixed complementarity problem (LMMCP) solver and the way of writing the condition as outlined in the dynare manual (http://www.dynare.org/manual/index_26.html). It still doesn´t work although I am in a deterministic setting.
Does anyone have a clue why this is happening? Help would be greatly appreciated.