209 research outputs found
Equation of Motion for the Solvent Polarization Apparent Charges in the Polarizable Continuum Model: Application to Time-Dependent CI
The dynamics of the electrons for a molecule in solution is coupled to the
dynamics of its polarizable environment, i.e., the solvent. To theoretically
investigate such electronic dynamics, we have recently developed equations of
motion (EOM) for the apparent solvent polarization charges that generate the
reaction field in the Polarizable Continuum Model (PCM) for solvation and we
have coupled them to a real-time time-dependent density functional theory (RT
TDDFT) description of the solute [Corni et al. J. Phys. Chem. A 119, 5405
(2014)]. Here we present an extension of the EOM-PCM approach to a
Time-Dependent Configuration Interaction (TD CI) description of the solute
dynamics, which is free from the qualitative artifacts of RT TDDFT in the
adiabatic approximation. As tests of the developed approach, we investigate the
solvent Debye relaxation after an electronic excitation of the solute obtained
either by a pulse of light or by assuming the idealized sudden promotion
to the excited state. Moreover, we present EOM for the Onsager solvation model
and we compare the results with PCM. The developed approach provides
qualitatively correct real-time evolutions and is promising as a general tool
to investigate the electron dynamics elicited by external electromagnetic
fields for molecules in solution.Comment: This is the final peer-reviewed manuscript accepted for publication
in The Journal of Chemical Physics. Copyright by AIP, the final published
version can be found at
http://scitation.aip.org/content/aip/journal/jcp/146/6/10.1063/1.497562
Analytical calculation of pressure for confined atomic and molecular systems using the eXtreme-Pressure Polarizable Continuum Model
We show that the pressure acting on atoms and molecular systems within the
compression cavity of the eXtreme-Pressure Polarizable Continuum method can be
expressed in terms of the electron density of the systems and of the
Pauli-repulsion confining potential. The analytical expression holds for
spherical cavities as well as for cavities constructed from van der Waals
spheres of the constituting atoms of the molecular systems
Correction: Absolute stereochemistry and preferred conformations of urate degradation intermediates from computed and experimental circular dichroism spectra
Correction for 'Absolute stereochemistry and preferred conformations of urate degradation intermediates from computed and experimental circular dichroism spectra' by Silvio Pipolo et al., Org. Biomol. Chem., 2011, 9, 5149â5155
Relating atomic energy, radius and electronegativity through compression
Trends in atomic properties are well-established tools for guiding the analysis and discovery of materials. Here, we show how compression can reveal a long sought-after connection between two central chemical concepts - van-der-Waals (vdW) radii and electronegativity - and how these relate to the driving forces behind chemical and physical transformations
Varying Electronic Configurations in Compressed Atoms: From the Role of the Spatial Extension of Atomic Orbitals to the Change of Electronic Configuration as an Isobaric Transformation
A quantum chemical model for the study of the electronic structure of compressed atoms lends itself to a perturbation-theoretic analysis. It is shown, both analytically and numerically, that the increase of the electronic energy with increasing compression depends on the electronic configuration, as a result of the variable spatial extent of the atomic orbitals involved. The different destabilization of the electronic states may lead to an isobaric change of the ground-state electronic configuration, and the same first-order model paves the way to a simple thermodynamical interpretation of this process
Formation and relaxation of excited states in solution: A new time dependent polarizable continuum model based on time dependent density functional theory
In this paper a novel approach to study the formation and relaxation of excited states in solution is presented within the integral equation formalism version of the polarizable continuum model. Such an approach uses the excited state relaxed density matrix to correct the time dependent density functional theory excitation energies and it introduces a state-specific solvent response, which can be further generalized within a time dependent formalism. This generalization is based on the use of a complex dielectric permittivity as a function of the frequency, ΔË(Ï). The approach is here presented in its theoretical formulation and applied to the various steps involved in the formation and relaxation of electronic excited states in solvated molecules. In particular, vertical excitations (and emissions), as well as time dependent Stokes shift and complete relaxation from vertical excited states back to ground state, can be obtained as different applications of the same theory. Numerical results on two molecular systems are reported to better illustrate the features of the model
Object-Oriented Modeling and simulation of a TRIGA reactor plant with Dymola
This work presents the modeling and simulation of a TRIGA-Mark II pool-type reactor with Zirchonium-Hydryde and Uranium fuel immersed in light water, with Modelica object-oriented language, in Dymola simulation environment. The model encompasses the integrated plant system including the reactor pool and cooling circuits. The reactor pool plays a fundamental role in the system dynamics, through a thermal feedback effect on the reactor core neutronics. The pool model is tested against three experimental transients: simulation results are in good accordance with experimental data and provide useful information about the inertial effect of the water inventory on the reactor cooling
Estimation of Mycobacterium avium subsp. paratuberculosis load in raw bulk tank milk in Emilia-Romagna Region (Italy) by qPCR
Consumption of milk and dairy products is considered one of the main routes of human exposure to Mycobacterium avium subsp. paratuberculosis (MAP). Quantitative data on MAP load in raw cowsâ milk are essential starting point for exposure assessment. Our study provides this information on a regional scale, estimating the load of MAP in bulk tank milk (BTM) produced in EmiliaâRomagna region (Italy). The survey was carried out on 2934 BTM samples (88.6% of the farms herein present) using two different target sequences for qPCR (f57 and IS900). Data about the performances of both qPCRs are also reported, highlighting the superior sensitivity of IS900âqPCR. Seven hundred and eightyânine samples tested MAPâpositive (apparent prevalence 26.9%) by IS900 qPCR. However, only 90 of these samples were quantifiable by qPCR. The quantifiable samples contained a median load of 32.4 MAP cells mL (â1) (and maximum load of 1424 MAP cells mL (â1)). This study has shown that a small proportion (3.1%) of BTM samples from EmiliaâRomagna region contained MAP in excess of the limit of detection (1.5Â ĂÂ 10(1) MAP cells mL (â1)), indicating low potential exposure for consumers if the milk subsequently undergoes pasteurization or if it is destined to typical hard cheese production
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