• focused model
• QM/MM
• Raman
• Raman Optical Acitivity

This thesis project have dealt with the implementation of embedding models for the theoretical simulation of Raman and Raman Optical Activity spectroscopies.
In order to compute spectroscopic properties in aqueous solution, the most successful strategy to use has been the use of focused models. Among this class of approaches, quantum mechanics(QM)/ molecular mechanics (MM), that keeps an atomistic description of the solvent, has had great success. The basic assumption of QM/MM approaches is the partition of the whole system into a QM fragment and an MM part, then the fundamental point is to appropriately model the coupling term between the quantum and classical regions. In this project, two polarizable QM/MM models, in particular the Quantum Mechanics/Fluctuating charges (QM/FQ) and Quantum Mechanics/ Fluctuating charges and Fluctuating Dipoles (QM/FQFμ) models have been used and compared to describe Raman and Vibrational Raman Optical Activity (VROA) spectroscopies. In order to obtain geoemtry optimizations, first analytical derivatives have been implemented and with the aim of computing spectroscopic properties it was necessary to use the response theory and TD-DFT fotmalism. The implementation of the contributions of the two models to the response equation, the so-called TD-DFT equations, allow the computing of polarizability tensors needed for Raman and Raman Optical Activity. The code has been tested on R-methyloxirane, L-cysteine and L-serine.