Semiempirical calculations of first-order hyperpolarizabilities: testing the performance of different methods in comparison to experiment

Article Abstract:

A study examined two common semiempirical methods for the computation of frequency-dependent first-order hyperpolarizabilities using a data set of 200 various organic compounds. This research compared the performance of three parametrizations, namely, AM1, PM3 and CNDOS, and two different approaches, namely, the sum-over-state approach and the time-dependent Hartree-Fock method. Despite the slight difference in the correlation coefficients, all the computational methods were found to be applicable to trend predictions in the molecular design of new compounds for nonlinear optical purposes.

Molecular computing, Nonlinear mechanics, Chaos theory

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Ab initio self-consistent calculations of the polarizibility and related functions of cubic SiC

Article Abstract:

A novel method for calculating the ab initio polarizability of chemicals was developed in an attempt to provide an effective means of determining the dielectric constant, reflectance and energy-loss function spectra of cubic silicone carbide (SiC). The proposed method makes use of the linear combination of atomic orbitals-self consistent field method to determine the ground state properties of SiC. Although the method manifested negligible energy location discrepancies, it generated spectra equivalents which are closely related to standard measures.

Electric properties, Polarization (Electricity), Silicon carbide, Silicon carbides, Atomic orbitals

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The development of replica- exchange-based free-energy methods

Article Abstract:

New free energy techniques that combine the advantages of the replica-exchange method with free- energy perturbation (FEP) and finite-difference thermodynamic integration (FDTI) are developed .The results of this application show that finite-difference thermodynamic integration (FDTI) has little hysteresis, although its standard errors and random sampling error are comparable to those of free-energy perturbation (FEP).

United States, Methods, Comparative analysis, Gibbs' free energy, Thermodynamic potentials

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