A Multichannel Least-Squares B-Spline Approach to Molecular Photoionization: Theory, Implementation, and Applications within the Configuration-Interaction Singles Approximation

We describe, in detail, a basis set approach to the multichannel scattering problem. The full set of linearly independent scattering states at each prefixed energy of the continuum spectrum can be obtained via a least-squares approach. To test the algorithm in a concrete setup, we report a parallel implementation of the close-coupling method in which the final states are treated within the configuration-interaction singles (CIS) approximation. The method requires, as input, a set of orthonormal orbitals, obtained from any quantum chemistry package. A one-center expansion (OCE) basis set consisting of products of radial B-splines and symmetry adapted angular functions is then used to expand the continuum electron wave function. To assess the quality of the CIS approximation, we compute total and partial cross sections and angular asymmetry parameters for the photoionization of a selection of closed-shell atoms (He, Ne, and Ar), H2, H2O, and ethylene. Results are compared with the experimental data and with theoretical predictions obtained with time-dependent density functional theory (TDDFT). It is seen that, generally, the photoionization observables obtained at the CIS level compare well with TDDFT predictions. The same basis can be employed to describe molecular multiphoton or strong field ionization

Accurate Vertical Excitation Energies of BODIPY/Aza-BODIPY Derivatives from Excited-State Mean-Field Calculations

We report a benchmark study of vertical excitation energies and oscillator strengths for the HOMO -> LUMO transitions of 17 boron-dipyrromethene (BODIPY) structures, showing a large variety of ring sizes and substituents. Results obtained at the time-dependent density functional theory (TDDFT) and at the delta-self-consistent-field (Delta SCF) by using 13 different exchange correlation kernels (within LDA, GGA, hybrid, and range-separated approximations) are benchmarked against the experimental excitation energies when available. It is found that the time-independent Delta SCF DFT method, when used in combination with hybrid PBE0 and B3LYP functionals, largely outperforms TDDFT and can be quite competitive, in terms of accuracy, with computationally more costly wave function based methods such as CC2 and CASPT2

Dynamical effects in the vibrationally resolved C 2s-1 photoionization cross section ratios of Methane

The vibrationally resolved C 2s photoionization cross-section of methane was investigated both theoretically and experimentally. When compared to that of C 1s photoionization, a rather different pattern has been observed, suggesting a strong interplay between the electron diffraction and interference effects

S 2p and P 2p Core Level Spectroscopy of PPT Ambipolar Material and Its Building Block Moieties

The near-edge X-ray absorption fine structure (NEXAFS and X-ray photoelectron (XP) spectra of gas-phase 2,8-bis-(diphenylphosphoryl)dibenzo[b,d]thiophene (PPT) and triphenylphosphine oxide (TPPO) have been measured at the S and P L-II,L-III-edge regions. The time-dependent density functional theory (TDDFT) based on the relativistic two-component zeroth-order regular approximation approach has been used to provide an assignment of the experimental spectra, giving the contribution of the spin-orbit splitting and of the molecular-field splitting to the sulfur and phosphor binding energies. Computed XP and NEXAFS spectra agree well with the experimental measurements. In going from dibenzothiophene and TPPO to PPT, the nature of the most intense S 2p and P 2p NEXAFS features are preserved; this trend suggests that the electronic and geometric behaviors of the S and P atoms in the two building block moieties are conserved in the more complex system of PPT. This work enables us to shed some light onto the structure of the P-O bond, a still highly debated topic in the chemical literature. Since the S 2p and P 2p NEXAFS intensities provide specific information on the higher-lying localized sigma*(C-S) and sigma*(P-O) virtual MOs, we have concluded that P 3d AOs are not involved in the formation of the P-O bond. Moreover, the results support the mechanism of negative hyperconjugation, by showing that transitions toward sigma*(P-O) states occur at lower energies with respect to those toward it pi*(P-O) states

Development of a Selective Wet-Chemical Etchant for 3D Structuring of Silicon via Nonlinear Laser Lithography

Recently-demonstrated high-quality three-dimensional (3D) subsurface laser processing inside crystalline silicon (c-Si) wafers opens a door to a wide range of novel applications in multidisciplinary research areas. Using this technique, a novel maskless micro-pillars with precise control on the surface reflection and coverage are successfully fabricated by etching the laser processed region of c-Si wafer. To achieve this, a particular selective wet chemical etching is developed to follow subsurface laser processing of c-Si to reveal the desired 3D structures with smooth surfaces. Here, we report the development of a novel chromium-free chemical etching recipe based on copper nitrate, which yields substantially smooth surfaces at high etch rate and selectivity on the both laser-processed Si surface and subsurface, i.e., without significant etching of the unmodified Si. Our results show that the etch rate and surface morphology are interrelated and strongly influenced by the composition of the adopted etching solution. After an extensive compositional study performed at room temperature, we identify an etchant with a selectivity of over 1600 times for laser-modified Si with respect to unmodified Si. We also support our findings using density functional theory calculations of HF and Cu adsorption energies, indicating significant diversity on the c-Si and laser-modified surfaces

Carbon and Nitrogen K-Edge NEXAFS Spectra of Indole, 2,3-Dihydro-7-azaindole, and 3-Formylindole

The near-edge X-ray absorption fine structure (NEXAFS) spectra of indole, 2,3-dihydro-7-azaindole, and 3-formylindole in the gas phase have been measured at the carbon and nitrogen K-edges. The spectral features have been interpreted based on density functional theory (DFT) calculations within the transition potential (TP) scheme, which is accurate enough for a general description of the measured C 1s NEXAFS spectra as well as for the assignment of the most relevant features. For the nitrogen K-edge, the agreement between experimental data and theoretical spectra calculated with TP-DFT was not quite satisfactory. This discrepancy was mainly attributed to the many-body effects associated with the excitation of the core electron, which are better described using the time-dependent density functional theory (TDDFT) with the range-separated hybrid functional CAM-B3LYP. An assignment of the measured N 1s NEXAFS spectral features has been proposed together with a complete description of the observed resonances. Intense transitions from core levels to unoccupied antibonding π* states as well as several transitions with mixed-valence/Rydberg or pure Rydberg character have been observed in the C and N K-edge spectra of all investigated indoles

Data identification of drug use in medical prescriptions of a private hospital at Campo Grande, Mato Grosso Do Sul, Brazil

Rational prescription occurs when patients receive the appropriate drug in adequate dose for the necessary period of time and it represents the safest and cheaper pharmacotherapy. The aim of this study was to identify the information about drug use in medical prescriptions at a private hospital. It was prescribed 2100 medicines between March 2006 and February 2007 and 44.48 % of these were prescribed by Generic medication name. The average number of drugs per prescription was 7.42. Prescriptions of at least one injectable drug or antibiotic were found in 58,00 % and 80,20 % of prescriptions, respectively. Half of prescribed drugs were part of the National List of Essential Drugs (50,33 %) and the Municipal List of Essential Drugs (55,24 %), both version 2006. The prevailing therapeutic classes were the analgesics (8.09 %) and anti-emetics (4.61 %). Incomplete medical prescriptions difficult drug use and hinder the service efficiency, putting at risk the quality of user assistance.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Electronic properties of the boroxine–gold interface: evidence of ultra-fast charge delocalization

We performed a combined experimental and theoretical study of the assembly of phenylboronic acid on the Au(111) surface, which is found to lead to the formation of triphenylboroxines by spontaneous condensation of trimers of molecules. The interface between the boroxine group and the gold surface has been characterized in terms of its electronic properties, revealing the existence of an ultra-fast charge delocalization channel in the proximity of the oxygen atoms of the heterocyclic group. More specifically, the DFT calculations show the presence of an unoccupied electronic state localized on both the oxygen atoms of the adsorbed triphenylboroxine and the gold atoms of the topmost layer. By means of resonant Auger electron spectroscopy, we demonstrate that this interface state represents an ultra-fast charge delocalization channel. Boroxine groups are among the most widely adopted building blocks in the synthesis of covalent organic frameworks on surfaces. Our findings indicate that such systems, typically employed as templates for the growth of organic films, can also act as active interlayers that provide an efficient electronic transport channel bridging the inorganic substrate and organic overlayer

İki Boyutlu Sistemler ile Au Arayüzlerinin Nanotribolojik Özellikleri Üzerine Teorik ve Deneysel Bir Çalışma

TÜBİTAK MFAG Proje01.04.20192015 yılında yayınlanan bir rapora göre dünya enerji üretiminin yaklaşık beşte biri sürtünmesonucu kaybolmaktadır. Özellikle otomotiv sanayisinde bu kaybın 2012 yılı itibarıyla, toplammaliyetin üçte birine kadar çıkabildiği belirtilmiştir. Gerek çevre kirliliğini azaltmak, gereksesürtünme sonucunda ortaya çıkan aşınmayı yavaşlatmak açısından, malzemeler arasındakisürtünme kuvvetlerinin davranışının anlaşılması ve azaltılması son derece önemlidir.Leonardo Da Vinci ile başlayıp Amontons ve Coulomb?a kadar uzanan ve triboloji olarakadlandırılan sürtünme ve aşınma çalışmalarında gelinen en son nokta, sürtünmenin atomistiközelliklerinin ele alınması olmuştur.Gittikçe küçülen skalalarda üretim teknolojilerinin ilerlemesiyle beraber nanoboyuttakisistemler ulaşılabilir hale gelmiştir. Grafit ve diğer katmansal yapılar, katmanlar arasındakietkileşmenin küçük olmasından dolayı iyi birer kaydırıcı malzeme adayıdır. Gerçekten degrafenin katmanları arasındaki sürtünme katsayısının konvansiyonel malzemelere göre çokdaha düşük olduğu kanıtlanmıştır.Literatürde bu tür iki boyutlu sistemlerin kendi aralarında oluşturduğu arayüzlerin sürtünmedavranışı üzerine birçok çalışma olsa da bu malzemelerle metal yüzeyleri arasındakiarayüzler üzerine incelemeler çok daha azdır. Projemizde, literatürdeki bu açığın giderilmesiamacıyla altın (Au) ve iki boyutlu sistemler arasındaki çeşitli arayüzlerin tribolojik özelliklerihem deneysel hem de teorik olarak ele alınmıştır. Teorik olarak yük yoğunluğu fonksiyoneliteorisi (DFT) ve moleküler dinamik (MD); deneysel olarak ise atomik kuvvet mikroskopisi(AKM) ile gerçekleştirilen çalışmalarımızda grafen/Au, h-BN/Au ve MoS2/Au arayüzlerininözellikleri incelenmiştir. Ayrıntılı sonuçlarımızdan her üç katmanlı materyalin de Au ile olanarayüzünde son derece düşük bir sürtünme katsayısına sahip olduğu ıspatlanmıştır. Hemyığın Au hem de Au kümeleri ile olan arayüz incelenmiş, böylelikle proje önerimizde debahsettiğimiz büyüklüğün etkisi incelemesi de gerçekleştirilmiştir. Çalışmalarımızdan üç adettez ve çok sayıda bildiri çıkmıştır. Makalelerimiz yayına hazır duruma getirilmiştir.According to a report published in 2015, approximately one fifth of Earth’s entire energy outputis lost to friction (Holmberg and Erdemir, 2015). Especially in the automotive industry, this losscan reach up to one third of the entire cost (Holmberg vd., 2012). It is therefore of utmostimportance to understand the mechanisms that go into creating friction, both for the reduction ofthe carbon footprint of these industries and to reduce material loss through wear. The final pointof a long line of research starting with Leonardo da Vinci and extending to Amontons andCoulomb, is the investigation of these mechanisms at the atomistic level.Thanks to the immense advanced in manufacturing technologies, nanoscale systems havebecome accessible. Graphite and similar layered materials have been predicted to demonstratesuperior lubrication properties due to the weak interactions between their layers. Indeed, thefriction coefficient between graphene layers have proven to be significantly lower thanconventional materials (Berman et al., 2014).The friction force between graphene-like two-dimensional materials have been rigorouslyinvestigated. However, the interface between these materials and metals remains significantlyunexplored. In our project, we investigated in detail the interface between Au andtwo-dimensional materials both experimentally and numerically in order to bridge this gap in theliterature. We have investigated the graphene/Au, h-BN/Au and MoS2/Au interfaces within thedensity functional theory (DFT) and molecular dynamics (MD) frameworks numerically andusing atomic force microscopy (AFM) experimentally. Our detailed results prove that all threeinterfaces present significantly low friction coefficients. In addition to the bulk interfaces,interfaces between Au clusters and bulk two-dimensional substrates have been studied in orderto shed light on the important size effects. We have published two theses and made twopresentations. Our papers are being prepared for publication with one ready to be publishedshortly

Theoretical Description of Many- Electron Processes in Photoionization (Fotoiyonizasyonda Çok Elektronlu Süreçlerin Teorik Olarak İncelenmesi)

TÜBİTAK MFAG Proje15.04.2016Bu raporda, projemizin konusu olan fotoiyonlaşma süreçlerinde çeşitli önemli özelliklerin hesaplanması için gerekli olan ve sürekli spektrumda tanımlanmış bir enerjiye denk gelen saçılma dalga fonksiyonlarının inşa edilmesi için geliştirilen çok-kanallı, least-squares metodu ayrıntılarıyla anlatılmaktadır. Bu algoritmanın detaylı bir şeklide test edilmesini sağlamak için bir close-coupling (CC) implementasyonu yapılmış ve MPI kullanılarak paralelleştirilmiştir. Metodda hedef durumlar configuration interaction singles (CIS) yaklaşımı kullanarak tanımlanmıştır. Metod, başlangıç olarak, ortonormal bir orbital setine ihtiyaç duymaktadır. Bu orbitaller MOLPRO gibi birçok yaygın kuantum kimyası paketinden elde edilebilir. Başlangıç orbitallerinin elde edilmesini takiben, tek merkezli açılım (OCE) baz fonksiyonları kullanılarak süreç sonucunda serbest kalan fotoelektronun dalga fonksiyonunun açılımı yapılır. Bizim çalışmamızda kullanılan baz fonksiyonları radyal B-spline’lar ile simetri-adapte açısal fonksiyonların çarpımıdır. Bu yaklaşımın doğrulunu test edebilmek için He, Ne, Ar, He, H2, H2O ve etilen gibi küçük ve orta ölçekli sistemlerde fotoiyonlaşma kesit alanı ve küresel simetri olmadığı durumlarda asimetri parametresi hesaplanmıştır. Sonuçlar hem deneysel hem de daha önce yapılmış zamana bağlı yük yoğunluğu fonksiyoneli (TDDFT) hesaplarıyla çok iyi bir uyum içindedir. Metodumuzun test ve paralelleştirme işlemleri devam etmektedir. Bundan sonra atılacak adım, daha da büyük sistemlerin incelenebilmesi için gerekli olan merkez-dışı (OCE ötesi) iki-elektron integrallerinin hesaplanmasıdır. Bunun yapılabilmesi için ise algoritmanın yeni baştan düşünülmesi gerekmektedir.In this report, we describe in detail a multichannel least squares approach which is used to efficiently obtain the full set of linearly independent scattering states at each prefixed energy of the continuum spectrum. To test the algorithm in a concrete setup, we report a parallel implementation of the close-coupling method in which the final states are treated within the configuration interaction singles (CIS) approximation. The method requires as input a set of orthonormal orbitals, obtained from any quantum chemistry package. A one-center expansion (OCE) basis set consisting of products of radial B-splines and symmetry adapted angular functions is then used to expand the photoelectron wave function. To assess the quality of the CIS approximation we compute total cross sections and angular asymmetry parameters for the photoionization of a selection of closedshell atoms (He, Ne, and Ar), H2, H2O, and ethylene. Results are compared with the experimental data and with theoretical predictions obtained with timedependent density functional theory (TDDFT). It is seen that generally the photoionization observables obtained at the CIS level compare well with TDDFT predictions