Study of time-dependent molecular properties for nanocomputing

Molecular Field-Coupling Nanocomputing (mFCN) stands out as a promising solution to address the challenges associated with CMOS scaling. The mFCN uses the charge distribution of molecules to encode information, which is then transmitted through electrostatic intermolecular interactions. This cutting-edge technology offers the potential for achieving switching frequencies in the order of terahertz at room temperature while minimizing power dissipation. At present, the conducted studies have successfully provided a comprehensive understanding of the static behavior related to the propagation of information through molecules in mFCN technology. However, there is a limited investigation into the dynamic aspects related to the transient response of the molecules involved, in particular for what concerns the dynamic of the electronic motion in mFCN technology. This thesis explores the dynamic of electronic motion to gain insights into the actual frequency capabilities of mFCN technology. To reach this goal, this thesis investigates the use of quantum chemistry methods. Specifically, Real-Time Time-Dependent Density Functional Theory (RTTDDFT) is employed for the first time for analyzing the dynamics of the molecules used in the mFCN. Initially, we verify the effectiveness of the computational techniques through the analysis of the water molecule. Subsequently, we examine the diallyl butane molecule to further validate the usefulness of these techniques in understanding and characterizing dynamic behavior. Firstly, we establish a local transfer function for the dipole moment of the water molecule, examining how it responds to electric fields with delta-like characteristics. Secondly, we derive a local transfer function for the diallyl butane molecule, focusing on its response to resonant, impulsive, and delta-like electric fields. Finally, we construct the corresponding Bode diagram for the diallyl butane molecule. The Bode diagram enables a high-level, electronic-based analysis of the molecule, characterizing it as an electronic device. This novel bottom-up approach brings a new perspective to the dynamic analysis of molecules not only in the context of mFCN but across the entire field of molecular electronics. Furthermore, it holds the potential for future integration of device-level results into a comprehensive system-level understanding. The outcomes derived from the analyses validate the expectations and go beyond them, as the molecules demonstrate the capability to achieve switching frequencies in the range of hundreds of terahertz. This implies that the true constraints on the speed of information propagation in the mFCN are not determined by electronic motion, but rather may be attributed either to the vibrational limitations of the nuclei, the capacity to generate such elevated frequencies to activate the molecules, or the limitations arising from intermolecular interactions. This thesis shows pioneering results in the mFCN field, as it delves into the dynamic investigation of candidate molecules for the first time. The single-molecule timing models contribute to the enrichment of the self-consistent electrostatic potential algorithm (SCERPA) for what concerns the time analysis of molecular FCN circuits.