China
Africa
Explore chapters and articles related to this topic
Simulation at Atomic Scale
Published in Chinmay K. Maiti, Fabless Semiconductor Manufacturing, 2023
A molecule is a stable arrangement of a group of nuclei and electrons. The exact arrangement can be described by electromagnetic force and quantum mechanical laws. Another picture of a molecule as a stable structure formed by the association of two or more atoms. In this case, the atoms retain their identity, whereas in the first case it is not. When a molecule is formed by using two atoms, the inner shell electron of each atom may be tightly bound to the nucleus or barely distributed. The outermost loosely bound electrons are known as valance electrons, are influenced by particles. The wave function is significantly modified when the atoms are brought together. The interatomic force is the electromagnetic interaction; hence the valance electron plays the important role in molecular binding. There are two main types of molecular binding, i.e., the ionic bond and the covalent bond. NaCl is a molecule held together by an ionic bond, whereas binding in an H2 molecule is a covalent bond having the energy of the Coulombic interaction of ions.
Molecularly imprinted bacterial cellulose for sustained-release delivery of quercetin
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Chutima Jantarat, Kanokkorn Attakitmongkol, Supirada Nichsapa, Pornpak Sirathanarun, Suthon Srivaro
Molecularly imprinted polymer (MIP) is an interesting material that is being used in combination with BC to improve the drug loading capacity and controlled drug release properties of BC. It is produced by introducing the template molecule of a desired substance during the process of polymer synthesis. After extracting the template molecule from the polymer, a molecular recognition site within the polymer that is specific for molecular binding with the template molecule in terms of size, shape, and functional group is created. Therefore, MIP can be used as an excipient in drug delivery for control drug release because a desired molecule can bind to it [14,15]. MIP has been shown to be potentially useful in sustained-release drug delivery [16,17]. In a previous study by Tamahkar et al. [18], drug release was found to be controlled more effectively from an MIP composite BC than from a non-imprinted polymer (NIP) composite BC.
Born–Oppenheimer potentials for Π, Δ, and Φ states of the hydrogen molecule
Published in Molecular Physics, 2022
Michał Siłkowski, Krzysztof Pachucki
All the potential curves have a well-pronounced single minimum around R = 2 au and exhibit strong features of anticrossings and curve interactions in the region au, which are associated with the configuration mixing. Those interactions have a trend to become weaker with the increasing angular momentum of the excited electron. Due to the high accuracy of the calculated potential, the dominating electronic configuration can be deduced from comparison to energies of helium atom excited states and of an infinitely separated hydrogen H()–H(nl) atoms. In particular, we observe, by reaching internuclear distances as small as R = 0.01 au, that the energies smoothly evolve to the corresponding value of the excited He atom [33]. It follows from the analysis of curves that each highly excited molecular state is dominated by a single atomic configuration at both the united atom and the dissociation limit. The nl configuration at both of those limits is usually not the same; therefore, in such cases, when considering fixed n in the molecular term (i.e. the nth eigenvalue of the BO molecular Hamiltonian), a character change of the excited electron has to occur at least once along the PEC. Understanding of the electronic character of a molecule in terms of singly excited atomic configurations originates from the pioneering works on the molecular binding theory of Hund, Mulliken and many others [34–36] and can be qualitatively described with the correlation diagrams [37]. Detailed analysis of electronic characters along the PECs is out of the scope of the current report and in this work we mainly focus on the computational aspects and accuracy comparison with previous ab-initio results. For a meticulous analysis of electronic configuration evolution as a function of n and R, we refer to the extensive analysis of Corongiu and Clementi [38].