Teaching Physicians Procedural Skills at a National Professional Meeting

Background: Practicing physicians often wish to improve their procedural skills but have limited educational opportunities to do so. Description: To summarize the effects of two procedural workshops on participants’ confidence, proficiency, and practice patterns. Evaluation: Following completion of a skin biopsy or arthrocentesis workshop, participants completed a post-course and an 8-month follow up evaluation. Recipients of this training rated it highly and reported that following training they performed more procedures, referred less, and noted an increase in their confidence that was still evident eight months after the workshop. Conclusion: Skin biopsy and arthrocentesis/joint injection skills can be taught to practicing physicians in a workshop setting at national professional meetings. Key Words: clinical competence; internal medicine; teaching; educational measuremen

Electronic Structure Methods for the Investigation of Nonadiabatic Dynamics

A detailed understanding of the interface between nuclear dynamics and electronic structure is crucial for describing excited state dynamics in photoexcited systems, a key aspect of modelling the efficiency of photovoltaic devices, among other applications. There has been a proliferation of techniques for approaching the problem of electronic-nuclear interactions from the perspective of both electronic structure and nuclear dynamics; the work presented here focuses on the electronic part of the equation. Methods are developed for alternative electronic representations, called diabatic representations, that anticipate the effects of nuclear momentum and attempt to minimize them. Diabatic representations can also be used to describe the electronic states involved in charge transfer or energy transfer processes, providing couplings necessary for approximating rates using Marcus theory. In addition, analytic techniques are developed that measure the impact of nuclear motion on electronic states, which can be used in the context of a dynamics simulation to approximate rates of energy transfer, charge transfer, or other types of internal conversion in chemical systems for which Marcus theory is insufficient. These methods are then used to couplings and rates for triplet-triplet energy transfer and singlet fission systems

Derivative couplings and analytic gradients for diabatic states, with an implementation for Boys-localized configuration-interaction singles

We demonstrate that Boys-localized diabatic states do indeed exhibit small derivative couplings, as is required of quasidiabatic states. In doing so, we present a general formalism for calculating derivative couplings and analytic gradients for diabatic states. We then develop additional equations specific to the case of Boys-localized configuration-interaction singles (CIS)—in particular, the analytic gradient of the CIS dipole matrix—and we validate our implementation against finite-difference results. In a forthcoming paper, we will publish additional algorithmic and computational details and apply our method to the Closs energy-transfer systems as a further test of the validity of Boys-localized diabatic states

Derivative couplings and analytic gradients for diabatic states, with an implementation for Boys-localized configuration-interaction singles

We demonstrate that Boys-localized diabatic states do indeed exhibit small derivative couplings, as is required of quasidiabatic states. In doing so, we present a general formalism for calculating derivative couplings and analytic gradients for diabatic states. We then develop additional equations specific to the case of Boys-localized configuration-interaction singles (CIS)—in particular, the analytic gradient of the CIS dipole matrix—and we validate our implementation against finite-difference results. In a forthcoming paper, we will publish additional algorithmic and computational details and apply our method to the Closs energy-transfer systems as a further test of the validity of Boys-localized diabatic states

Analytic derivative couplings between configuration-interaction-singles states with built-in electron-translation factors for translational invariance

We present a method for analytically calculating the derivative couplings between a pair of configuration-interaction-singles (CIS) excited states obtained in an atom-centered basis. Our theory is exact and has been derived using two completely independent approaches: one inspired by the Hellmann-Feynman theorem and the other following from direct differentiation. (The former is new, while the latter is in the spirit of existing approaches in the literature.) Our expression for the derivative couplings incorporates all Pulay effects associated with the use of an atom-centered basis, and the computational cost is minimal, roughly comparable to that of a single CIS energy gradient. We have validated our method against CIS finite-difference results and have applied it to the lowest lying excited states of naphthalene; we find that naphthalene derivative couplings include Pulay contributions sufficient to have a qualitative effect. Going beyond standard problems in analytic gradient theory, we have also constructed a correction, based on perturbative electron-translation factors, for including electronic momentum and eliminating spurious components of the derivative couplings that break translational symmetry. This correction is general and can be applied to any level of electronic structure theory

Derivative couplings between TDDFT excited states obtained by direct differentiation in the Tamm-Dancoff approximation

Working within the Tamm-Dancoff approximation, we calculate the derivative couplings between time-dependent density-functional theory excited states by assuming that the Kohn-Sham superposition of singly excited determinants represents a true electronic wavefunction. All Pulay terms are included in our derivative coupling expression. The reasonability of our approach can be established by noting that, for closely separated electronic states in the infinite basis limit, our final expres- sion agrees exactly with the Chernyak-Mukamel expression (with transition densities from response theory). Finally, we also validate our approach empirically by analyzing the behavior of the derivative couplings around the T1/T2 conical intersection of benzaldehyde

Analysis of Localized Diabatic States beyond the Condon Approximation for Excitation Energy Transfer Processes

In a previous paper [Fatehi, S.; et al. J. Chem. Phys. 2013, 139, 124112], we demonstrated a practical method by which analytic derivative couplings of Boys-localized CIS states can be obtained. In this paper, we now apply that same method to the analysis of triplet–triplet energy transfer systems studied by Closs and collaborators [Closs, G. L.; et al. J. Am. Chem. Soc.1988, 110, 2652]. For the systems examined, we are able to conclude that (i) the derivative coupling in the BoysOV basis is negligible, and (ii) the diabatic coupling will likely change little over the configuration space explored at room temperature. Furthermore, we propose and evaluate an approximation that allows for the inexpensive calculation of accurate diabatic energy gradients, called the “strictly diabatic” approximation. This work highlights the effectiveness of diabatic state analytic gradient theory in realistic systems and demonstrates that localized diabatic states can serve as an acceptable approximation to strictly diabatic states

TD-DFT spin-adiabats with analytic nonadiabatic derivative couplings

Wepresent an algorithm for efficient calculation of analytic nonadiabatic derivative couplings between spin-adiabatic, time-dependent density functional theory states within the Tamm-Dancoff approximation. Our derivation is based on the direct differentiation of the Kohn-Sham pseudowavefunction using the framework of Ou et al. Our implementation is limited to the case of a system with an even number of electrons in a closed shell ground state, and we validate our algorithm against finite difference at an S1/T2 crossing of benzaldehyde. Through the introduction of a magnetic field spin-coupling operator, we break time-reversal symmetry to generate complex valued nonadiabatic derivative couplings. Although the nonadiabatic derivative couplings are complex valued, we find that a phase rotation can generate an almost entirely real-valued derivative coupling vector for the case of benzaldehyde