: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Electronic structure and spectroscopy of nucleic acid bases: Ionization energies, ionization-induced structural changes, and photoelectron spectra Ksenia B. Bravaya a , Oleg Kostko b , Stanislav Dolgikh a , Arie Landau a , Musahid Ahmed b , and Anna I. Krylov a a Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482, USA b Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA We report high-level ab initio calculations and single-photon ionization mass spec- trometry study of ionization of adenine (A), thymine (T), cytosine (C) and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized ﬁve lowest-energy tautomeric forms. The ﬁrst adiabatic and several vertical ionization energies were computed us- ing equation-of-motion coupled-cluster method for ionization potentials with single and double substitutions. Equilibrium structures of the cationic ground states were characterized by DFT with the ωB97X-D functional. The ionization-induced geome- try changes of the bases are consistent with the shapes of the corresponding molecular orbitals. For the lowest-energy tautomers, the magnitude of the structural relaxation decreases in the following series G>C>A>T, the respective relaxation energies being 0.41, 0.32, 0.25 and 0.20 eV. The computed adiabatic ionization energies (8.13, 8.89, 8.51-8.67 and 7.75-7.87 eV for A,T,C and G, respectively) agree well with the on- sets of the photoionization eﬃciency (PIE) curves (8.20±0.05, 8.95±0.05, 8.60±0.05 and 7.75±0.05 eV). Vibrational progressions for the S 0 -D 0 vibronic bands computed within double-harmonic approximation with Duschinsky rotations are compared with previously reported experimental photoelectron spectra. I. INTRODUCTION Ionization of DNA bases is one of the processes involved in DNA radiation- and photo- damage resulting in dangerous mutations with potential risk for cancer and neurodegenera-

Electronic structure and spectroscopy of nucleic acid bases: Ionization energies, ionization-induced structural changes, and photoelectron spectra

The accuracy and efficiency of electronic-structure methods to understand, predict and design the properties of materials has driven a new paradigm in research Simulations can greatly accelerate the identification, characterization and optimization of materials, with this acceleration driven by continuous progress in theory, algorithms and hardware, and by adaptation of concepts and tools from computer science Nevertheless, the capability to identify and characterize materials relies on the predictive accuracy of the underlying physical descriptions, and on the ability to capture the complexity of realistic systems We provide here an overview of electronic-structure methods, of their application to the prediction of materials properties, and of the different strategies employed towards the broader goals of materials design and discovery Simulations can be used to accelerate the characterization and discovery of materials Here we Review how electronic-structure methods such as density functional theory work, what properties they can be used to predict and how they can be used to design materials

Electronic-structure methods for materials design.

Corannulene, a kind of bowl like polycyclic aromatic hydrocarbon (PAH), whose molecule is composed of a central pentagon and five closely adjacent hexagons on the pentagon's five sides, has received great scientific interest among research groups. In this review, the syntheses, characteristic molecule structure and properties of corannulene are clarified, as well as its derivatives with different substituted groups, fused derivatives, metal complex, and derivatives for host guest chemistry. On the basis of reviewing the applications and properties of corannulene together with its derivatives, the potential applications in hydrogen storage and lithium storage were highlighted and prospected.

Buckybowls: Corannulene and Its Derivatives.

The review summarizes data on dipole polarizability of fullerenes and their derivatives, covering the most widespread classes of fullerene-containing molecules (fullerenes, fullerene exohedral derivatives, fullerene dimers, endofullerenes, fullerene ions, and derivatives with ionic bonds). These are currently presented by experimental and mainly theoretical works. Particular attention is paid to the analysis of the computational data in terms of additive schemes that assist in understanding the changes in polarizability upon fullerene functionalization and provide a general formula for calculation of polarizability for certain classes of the exohedral derivatives. Additionally, application of polarizability to the physical and chemical problems of fullerene science is discussed. It includes aspects of fullerene reactivity, physicochemical processes in carbon nanostructures (quenching of electronically-excited states, nanocapillarity, etc.) as well as use of fullerene adducts as electron-acceptor materials for organic solar cells and molecular switch devices.

Polarizability as a landmark property for fullerene chemistry and materials science

Koopmans-compliant functionals have been shown to provide accurate spectral properties for molecular systems; this accuracy is driven by the generalized linearization condition imposed on each charged excitation - i.e. on changing the occupation of any orbital in the system, while accounting for screening and relaxation from all other electrons. In this work we discuss the theoretical formulation and the practical implementation of this formalism to the case of extended systems, where a third condition, the localization of Koopmans' orbitals, proves crucial to reach seamlessly the thermodynamic limit. We illustrate the formalism by first studying one-dimensional molecular systems of increasing length. Then, we consider the band gaps of 30 paradigmatic solid-state test cases, for which accurate experimental and computational results are available. The results are found to be comparable with the state-of-the-art in diagrammatic techniques (self-consistent many-body perturbation theory with vertex corrections), notably using just a functional formulation for spectral properties and the physics of the generalized-gradient approximation; when ionization potentials are compared, the results are roughly twice as accurate.

Koopmans-Compliant Spectral Functionals for Extended Systems

The need to interpret ultraviolet photoemission data strongly motivates the refinement of first-principles techniques that are able to accurately predict spectral properties. In this work, we employ Koopmans-compliant functionals, constructed to enforce piecewise linearity in approximate density functionals, to calculate the structural and electronic properties of DNA and RNA nucleobases. Our results show that not only ionization potentials and electron affinities are accurately predicted with mean absolute errors of <0.1 eV, but also that calculated photoemission spectra are in excellent agreement with experimental ultraviolet photoemission spectra. In particular, the role and contribution of different tautomers to the photoemission spectra are highlighted and discussed in detail. The structural properties of nucleobases are also investigated, showing an improved description with respect to local and semilocal density-functional theory. Methodologically, our results further consolidate the role of Koopma...

First-Principles Photoemission Spectroscopy of DNA and RNA Nucleobases from Koopmans-Compliant Functionals

First principles techniques are used to investigate the structure, linear polarizability, and field-oriented property trends of the series of bowl shaped polynuclear aromatic hydrocarbon fragments, C20H10, C30H10, C40H10, and C50H10 Such structures represent a sequence of minimalistic, capped bucky tube units based on the corannulene molecule, with interesting technological promise imparted by their curvature Specific issues associated with how the intrinsic dipole and static linear polarizability influences the orientation of these structures in the presence of an external electric field are addressed and shown to correlate well with a simple analytical model At moderate electric fields, the induced dipoles become comparable and even larger than the intrinsic dipoles due to the large in-plane polarizabilities in these systems This generates a nontrivial and field dependent orientation of the molecule that can be exploited, for example, to induce switching behavior within molecular nanojunctions

Static and Field-Oriented Properties of Bowl-Shaped Polynuclear Aromatic Hydrocarbon Fragments.

First-principles methodology based on density functional theory (DFT) is used to investigate charge transport phenomena in molecular junctions, with the central active molecular element based on corannulene, C20H10, assembled between two carbon nanotubes (CNT). A number of key factors associated with the design of the molecular nanojunction are shown to have an impact on electron transport to varying degrees, including (I) the composition of the spacer linking the leads to the active element, (II) the composition of the active molecule element, (III) the sensor capabilities of the active element, and (IV) the response of the junction to an external electric field. This study demonstrates the ability to integrate molecular electronic functionality into electronic nanocircuits and provides novel insight into the design of new types of molecular-based devices by revealing the relationship between charge transport mechanisms and the electronic structure of molecular junction components.

Andrea Ferretti

Papers

Koopmans-Compliant Spectral Functionals for Extended Systems

First-Principles Photoemission Spectroscopy of DNA and RNA Nucleobases from Koopmans-Compliant Functionals

Static and Field-Oriented Properties of Bowl-Shaped Polynuclear Aromatic Hydrocarbon Fragments.

Tuning Electron Transport through Functionalized C20H10 Molecular Junctions

Koopmans-compliant spectral functionals for extended systems