• ccsd
• chemistry
• Cholesky decomposition
• computational chemistry
• coupled-cluster
• electric dipoles
• electronic structure theory
• geometry optimizations
• gradients
• physical chemistry
• properties
• theoretical chemistry

Highly accurate calculations of molecular properties on single-reference systems require the inclusion of dynamic correlation effects within the quantum chemical treatment of choice. One of the most successful approaches in that regard is Coupled-Cluster (CC) theory which, due to size-extensivity and its inherent accuracy, is known as an almost "black box" scheme. CC methods are also characterized by a steep computational cost, both in terms of number of floating point operations and storage requirements. Memory especially is a limiting factor concerning the maximum size of the systems which can be reliably treated at the CC level.
However, the Cholesky Decomposition (CD) of the electron repulsion integral (ERI) matrix offers several advantages capable of reducing the impact of the aforementioned issues. The aim of this thesis is to extend the limits of applicability of calculations of first-order properties, namely electric dipoles and analytical gradients for geometry optimizations, for molecules up to twenty heavy atoms thanks to efficient numerical techniques based on the CD of ERIs.
In the present thesis, we have reformulated the theory behind such computations by applying the CD of two-electron integrals and developed an efficient implementation within the CFOUR suite of programs. Finally, we ran some numerical calculations in order to test our code, computing the BLA of several polyenes on optimized geometries, proving the efficiency of our program.