Search

International audience; This chapter describes the theoretical background of the quantum mechanical/molecular mechanical (QM/MM) implementation in deMon2k within the framework of auxiliary density functional theory (ADFT). It aims to give the reader an overview of the current state of the art of this QM/MM implementation and perspectives for its future development. To this end, we first derive the ADFT working equations for the QM and QM/MM energy and gradient expressions. Based on the joint QM/MM gradient expression, we present algorithms for QM/MM structure optimizations, transition-state searches and molecular dynamics simulations. The use of auxiliary density perturbation theory (ADPT) in the framework of QM/MM is discussed using illustrative implementations including analytic second-order ADFT energy derivatives, nuclear magnetic resonance chemical shift calculations and excited state calculations using time-dependent ADFT. The chapter closes with the description of a transformation program used to generate deMon2k QM/MM inputs.

In the current work, a new family of isoelectronic analogues to B12 is reported. The construction of this family was performed through the isoelectronic substitution principle to generate species such as B11C+, B11Be-, B10BeC, B10C22+, B10Be22- B9Be2C-, and B9BeC2+. The search for the global minimum was realized employing genetic algorithms, while the induced magnetic field, electronic localization function, magnetic current densities, and multicenter aromaticity criteria were calculated to understand their electronic delocalization. Our results show that, in general, C atoms avoid hypercoordination, whereas we have found species with Be atoms located in hypercoordinated positions that are relatively stable. Our analysis of aromaticity indicates that B12 has double and disk aromaticity. Mono, double or triple substitution of B by C+ or Be- reduces somewhat the aromaticity of the clusters, but less in the case of Be- substitution RI is grateful with Fondecyt 11160927 and Fondecyt 1201436 projects for the financial supporting. DI is grateful for the financial support by CONICYT PFCHA/DOCTORADO NACIONAL/2019 – 21190427. BZ-G acknowledges the financial support given by Conacyt Project (258647). This work has also been supported by the Ministerio de Economía y Competitividad (MINECO) of Spain (Projects CTQ2017-85341-P, CTQ2016-77558-R, and MDM-2017- 0767) and the Generalitat de Catalunya (projects 2017SGR39 and 2017SGR348, Xarxa de Referència en Química Teòrica i Computacional, and ICREA Academia 2014 prize for M.S.)