Molecular properties response methods

Calculations of time-dependent electromagnetic properties of molecules at the correlated electronic structure level are conveniently carried out by the utilization of modern response theory [43-51], The transition of modern response theory for gas phase molecular systems to solvated molecules has been established [1-6] and these methods include the use of correlated electronic wavefunctions. These methods, reviewed here, have given rise a large number of computational approaches for calculating electric and magnetic molecular properties of solvated molecules. 

Our present focus is on correlated electronic structure methods for describing molecular systems interacting with a structured environment where the electronic wavefunction for the molecule is given by a multiconfigurational self-consistent field wavefunction. Using the MCSCF structured environment response method it is possible to determine molecular properties such as (i) frequency-dependent polarizabilities, (ii) excitation and deexcitation energies, (iii) transition moments, (iv) two-photon matrix elements, (v) frequency-dependent first hyperpolarizability tensors, (vi) frequency-dependent polarizabilities of excited states, (vii) frequency-dependent second hyperpolarizabilities (y), (viii) three-photon absorptions, and (ix) two-photon absorption between excited states. 

The three Equations (4.108)—(4.110) are only true for exact wavefunctions and they do indeed provide crude and problematic methods for calculating molecular properties. The advantage of these equations is that they indicate what one is able to obtain from this method but for actual calculations of molecular properties using approximative wavefunctions, it is important to use modern versions of response theory where the summation over states is eliminated [1,10-14,88-90],... 

Based on the MCSCF/CM quadratic response method it is possible to calculate the hyperpolarizability tensor and the two-photon absorption cross-sections. The calculated MCSCF/CM properties exhibit for all the individual tensor components substantial shifts compared with the corresponding molecular properties of the molecule in vacuum. 

The MCSCF/CM response method provide procedures for obtaining frequency-dependent molecular properties when investigating a molecule coupled to a structured environment and the basis is achieved by treating the quantum mechanical subsystem on a quantum mechanical level and the structured environment as a classical subsystem described by a molecular mechanics force field. The important interactions between the two subsystems are included directly in the optimized wave function. 

Abstract The computational study of excited states of molecular systems in the condensed phase implies additional complications with respect to analogous studies on isolated molecules. Some of them can be faced by a computational modeling based on a continuum (i.e., implicit) description of the solvent. Among this class of methods, the polarizable continuum model (PCM) has widely been used in its basic formulation to study ground state properties of molecular solutes. The consideration of molecular properties of excited states has led to the elaboration of numerous additional features not present in the PCM basic version. Nonequilibrium effects, state-specific versus linear response quantum mechanical description, analytical gradients, and electronic coupling between solvated chromophores are reviewed in the present contribution. The presentation of some selected computational results shows the potentialities of the approach. 

We consider correlated electronic structure methods for molecular systems interacting with a structured environment and the utilization of response theory makes it possible to calculate molecular properties of the molecular subsystem coupled to an aerosol particle and the molecular properties could be... 

We have presented response methods that provide procedures for calculating frequency-dependent molecular properties for a molecular subsystem coupled to a stmctured environment. We have shown that the molecular subsystem is treated on a quantum mechanical level and the stmctured environment as a classical subsystem. We have presented the stmctured environment, classical subsystem, as a heterogeneous dielectric media or a molecular mechanics force field. We have demonstrated that the interactions between the quantum mechanical and classical subsystems are part of the energy functional used for optimizing the MCSCF electronic wave function. 

---