Stress and Vibrational Properties of non-local van der Waals exchange-correlation functionals

Van der Waals interaction is an essential component in the description of soft matter and plays an important role in many other systems, from adsorbates to water interaction. Within the framework of Density Functional Theory in the last years a great effort has been made to overcome the limitations of LDA or GGA functionals, and a new class of non-local functionals is now filling the gap giving interesting results. We present here several new improvements in this field, and some selected applications. In particular, i) we worked out the theoretical formalism needed to define both the stress tensor and the phonon vibrations associated to the non-local functional form proposed by Dion[1], and ii) we developed and implemented in the Quantum ESPRESSO simulation package a new functional inspired by the work of Vydrov and Van Voorhis[2], simple to compute efficiently in plane wave approach and with great performances on the S22 set. Finally we present some results obtained on aminoacid crystal and other simple molecules where these new tools are benchmarked and compared with experimental results and other theoretical approaches. \\[4pt] [1] M. Dion, B. I. Lundqvist et al., Phys. Rev. Lett. 92, 246401 (2004); \\[0pt] [2] Oleg A. Vydrov and Troy Van Voorhis , Phys. Rev. Lett. 103, 06300