39 research outputs found
Bias effects on the electronic spectrum of a molecular bridge
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98651/1/JChemPhys_134_054708.pd
Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package
This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design
Manifestations of Symmetry Breaking in Self-consistent Field Electronic Structure Calculations
Characterization of the Relevant Excited States in the Photodissociation of CO-Ligated Hemoglobin and Myoglobin
Solvated Charge Transfer States of Functionalized Anthracene and Tetracyanoethylene Dimers: A Computational Study Based on a Range Separated Hybrid Functional and Charge Constrained Self-Consistent Field with Switching Gaussian Polarized Continuum Models
We benchmark several protocols for evaluating the energies
of excited
charge transfer (CT) states of organic molecules dissolved in polar
liquids. The protocols combine time-dependent density functional theory
using range-separated hybrid functionals, constrained density functional
theory, dispersion corrected functional, and a dielectric continuum
model for representing the solvent. We compare the different protocols
against well-established experimental measured charge transfer state
energies in solvated dimers of functionalized anthracene and tetracyanoethylene.
We find that using the range-separated hybrid functional for the charge-transfer
state energies and the combination of constrained density functional
theory with the recently improved switching Gaussian polarizable continuum
model (PCM) provide good agreement with the experimental values of
the solvated CT states. We also find that using dispersion corrected
solvated geometries for the weakly coupled donor–acceptor dimers
considered here leads to improved agreement with experimental measured
values
The Effect of Interfacial Geometry on Charge-Transfer States in the Phthalocyanine/Fullerene Organic Photovoltaic System
The
dependence of charge-transfer states on interfacial geometry
at the phthalocyanine/fullerene organic photovoltaic system is investigated.
The effect of deviations from the equilibrium geometry of the donor–donor–acceptor
trimer on the energies of and electronic coupling between different
types of interfacial electronic excited states is calculated from
first-principles. Deviations from the equilibrium geometry are found
to destabilize the donor-to-donor charge transfer states and to weaken
their coupling to the photoexcited donor-localized states, thereby
reducing their ability to serve as charge traps. At the same time,
we find that the energies of donor-to-acceptor charge transfer states
and their coupling to the donor-localized photoexcited states are
either less sensitive to the interfacial geometry or become more favorable
due to modifications relative to the equilibrium geometry, thereby
enhancing their ability to serve as gateway states for charge separation.
Through these findings, we eludicate how interfacial geometry modifications
can play a key role in achieving charge separation in this widely
studied organic photovoltaic system
Donor-to-Donor vs Donor-to-Acceptor Interfacial Charge Transfer States in the Phthalocyanine–Fullerene Organic Photovoltaic System
Charge transfer (CT) states formed
at the donor/acceptor heterointerface
are key for photocurrent generation in organic photovoltaics (OPV).
Our calculations show that interfacial donor-to-donor CT states in
the phthalocyanine–fullerene OPV system may be more stable
than donor-to-acceptor CT states and that they may rapidly recombine,
thereby constituting a potentially critical and thus far overlooked
loss mechanism. Our results provide new insight into processes that
may compete with charge separation, and suggest that the efficiency
for charge separation may be improved by destabilizing donor-to-donor
CT states or decoupling them from other states