1 2 >> Category Quantum Chemistry |Investigation of excited states of organic compounds
Quantum chemical calculations of the electronic structure and geometry of the electronically excited molecules are widely used for the interpretation of experimental data and the classification of the absorption bands of the absorption spectra of communication with the structure of the molecule and its conformation, as well as to study the reactivity of molecules in photochemical reactions.
Intense absorption bands in the IR spectrum
The integrated intensity of the IR absorption bands for the pitch, as you know, is proportional to the square of the derivative of the dipole moment of the molecule to a normal coordinate ∂μ/∂Q 2 . Depending on the origin of the dipole moment of Q due to both the displacement of the atoms that carry a charge, and changes in the populations themselves charges or AO. To calculate the intensity is sufficient to calculate the dipole moment for equilibrium and nonequilibrium values of Q, which is significant technical difficulties is not, although it requires knowledge waveform.
MODEL point dipoles
The main drawback supermolecule approximation methods and Monte Carlo with the atom-atom potential is extremely complicated calculation. Therefore, it was natural for the appearance of methods that preserve the principle of these approaches, ie, taking into account explicitly the discrete set of solvent molecules around the solute compound, but simulating it with the point dipoles.
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