  Modeling electronic systems is an important application for quantum
computers. In the context of materials science, an important open problem is
the computational description of chemical reactions on surfaces. In this work,
we outline a workflow to model the adsorption and reaction of molecules on
surfaces using quantum computing algorithms. We develop and compare two local
embedding methods for the systematic determination of active spaces. These
methods are automated and based on the physics of molecule-surface interactions
and yield systematically improvable active spaces. Furthermore, to reduce the
quantum resources required for the simulation of the selected active spaces
using quantum algorithms, we introduce a technique for exact and automated
circuit simplification. This technique is applicable to a broad class of
quantum circuits and critical to enable demonstration on near-term quantum
devices. We apply the proposed combination of active-space selection and
circuit simplification to the dissociation of water on a magnesium surface
using classical simulators and quantum hardware. Our study identifies reactions
of molecules on surfaces, in conjunction with the proposed algorithmic
workflow, as a promising research direction in the field of quantum computing
applied to materials science.
