## Hybrid atomistic approach for ab initio molecular dynamics

** Daniele Loco**

Laboratoire de Chimie Théorique - UMR7616 UPMC & CNRS, Paris, France

Mercredi 21 Novembre 2018, 11h00

bibliothèque LCT, tour 12 - 13, 4^{ème} étage

In recent years lots of efforts have been devoted in the field of Classical Molecular Dynamics (MD) for the development of force fields that explicitly account for polarization, but still efficient for the study of large systems. They include many-body effects improving, in principle, flexibility and accuracy. Such improvement is still not enough for the description of many important phenomena in molecular science, such as chemical reactivity and light-driven processes, due to their intrinsic quantum nature. In that respect, hybrid approaches where a small portion of the system is treated at Quantum Mechanics level, while the rest according to the laws of Classical Mechanics, represent a promising strategy as they combine the computational efficiency of a classical model with the required quantum description of the subsystem of interest.

In this contribution we will present a hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) MD method, as implemented interfacing the Gaussian and Tinker suite of programs, to perform adiabatic Born-Oppenheimer (BO) dynamics in the electronic ground state of the quantum subsystem [1, 2]. Such approach is based on the coupling of Density Functional Theory (DFT) and the polarizable AMOEBA potential [3] through a variational formalism. The variational formulation of the QM/MM problem allows for a self-consistent relaxation of both the AMOEBA induced dipoles and the DFT electronic density at each MD step.

Furthermore we take advantage of an Extended Lagrangian formulation of the BOMD (XL-BOMD) [4], improving the initial guess for the SCF equations, using the informations available along the trajectory.

Test cases will be presented as benchmark for the performances of the code.

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**References :**

[1] D. Loco, E. Polack, S. Caprasecca, L. Lagardère, F. Lipparini, J.-P. Piquemal, and B. Mennucci, *J. Chem. Theory Comput.* **2016**, *12*, 3654.

[2] D. Loco, L. Lagardère, S. Caprasecca, F. Lipparini, B. Mennucci, and J.-P. Piquemal, *J. Chem. Theory Comput.* **2017**, *13*, 4025.

[3] J. W. Ponder, C. Wu, P. Ren, V. S. Pande, J. D. Chodera, M. J. Schnieders, I. Haque, D. L. Mobley, D. S. Lambrecht, R. A. DiStasio Jr, M. Head-Gordon, G. N. Clark, M. E. Johnson, and T. Head-Gordon, *J. Phys. Chem. B* **2010**, *114*, 2549.

[4] A. M. N. Niklasson, P. Steneteg, A. Odell, N. Bock, M. Challacombe, C. J. Tymczak, E. Holmstr&oauml;m, G. Zheng, and V. Weber, *J. Chem. Phys.* **2009**, *130*, 214109.