Simplified reaction models were developed theoretically and experimentally for use in the computational fluid dynamics of Gallium Nitride (GaN) growth in metal organic vapor-phase epitaxy (MOVPE). The activation energy of various elementary reaction pathways in a trimethylgallium/ammonia /hydrogen (Ga(CH3)(3)/NH3/H-2) system were calculated using an ab-initio molecular orbital (MO) method. Then, the dominant steps of the reaction paths and the respective activation energies were obtained using the following reactions: Ga(CH3) (3) + NH3 -> Ga(CH3)(2)NH2 (Ea = 1.3 eV), 2Ga(CH3)(2)NH2 -> [Ga(CH3)(2)NH2 ] (2) + 2CH(4) (Ea = 0 eV), Ga(CH3)(2)NH2 -> GaN + 2CH(4) (Ea = 3.0 eV). The computational fluid dynamics performed using our reaction-model agreed well with the experimental results for the distribution of the GaN growth rate under this study's growth conditions. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.jes034205] All rights reserved.