Here, we formulate the energy and analytic first derivatives of an additive electrostatic embedding DFTB/MM in PBC using particle mesh Ewald (PME) sums. Our DFTB/MM method is closely related to the PME/PME formulation by Nishizawa and Okumura, and Kubař, Welke and Groenhof, with an extension on the derivatives with respect to lattice parameters and the capping by link atoms. Without loss of generality, hereafter we focus on DFTB2 energy expression. The total DFTB/MM energy is defined as