I assume adsorption of molecules has been vastly studied in literature, using DFT-LCAO and PW, e.g., see J. Phys. Chem. B 2006 110, 45, 22628-22634 (2006),
https://doi.org/10.1021/jp0642847 . QuantumATK implements both DFT methods for norm-conserving pseudopotentials (LCAO, PW calculations) and PAW potentials for PW calcualtions. So, it covers a vast range of tools needed for this kind of study. I do not know what you exactly mean by accurate. I guess QuantumATK is able to handle this problem as accurate as DFT is able to, in general.
