Area Of Quantum Chemistry Research Articles

Excited State Search Using Quantum Annealing

Quantum annealing (QA) is one of the ways to search the ground state of the problem Hamiltonian. Here, we propose the QA scheme to search arbitrary excited states of the problem Hamiltonian. In our scheme, an $n$-th excited state of the trivial Hamiltonian is initially prepared and is adiabatically changed into an $n$-th excited state of the target Hamiltonian. Although our scheme is general such that we can search any excited states, we especially discuss the first excited state search in this paper. As a comparison, we consider a non-adiabatic scheme to find the first excited state with non-adiabatic transitions from the ground state. By solving the Lindblad master equation, we evaluate the performance of each scheme under the influence of decoherence. Our conclusion is that the adiabatic scheme show better performance than the non-adiabatic scheme as long as the coherence time of qubits is sufficiently long. These results are important for applications in the area of quantum chemistry, quantum simulation, and post-quantum cryptography.

An Introduction to Coding with Matlab: Simulation of X-ray Photoelectron Spectroscopy by Employing Slater’s Rules

Computational approaches toward simulating chemical systems and evaluating experimental data has gathered great momentum in recent years. The onset of more powerful computers and advanced software has been instrumental to this end. This manuscript presents a hands-on activity which trains students in basic coding skills within the Matlab framework. Moreover, students are able to simulate X-ray photoelectron spectroscopy (XPS) spectra of various elements using Slater’s rules, a cornerstone of computational chemistry and a key topic in many undergraduate courses. A semiworked cadmium XPS example is introduced herein from which the XPS binding energy of the 3d electron may be calculated. Results are then compared with experimental values. The close agreement (within 10%) offers a real sense of student satisfaction and an appreciation of the value of computational techniques. Further elements and electronic configurations are subsequently explored. In sum, this practical develops understanding in the areas of quantum chemistry, spectroscopy, and coding skills simultaneously.

Preface: Proceedings of the XV Brazilian Symposium of Theoretical Chemistry

The Brazilian Symposium of Theoretical Chemistry (SBQT) is a traditional scientific meeting in the area of Quantum Chemistry and Molecular Physics. This symposium occurs every two years. This 15th version gathered about 300 participants from several countries, mostly from Latin America. In this XV SBQT a total of 13 plenary and 40 short lectures were delivered. In addition, around 390 posters were presented, by both senior scientists as well as students. This issue collects a part of the scientific contributions presented at the meeting. This version occurred during the period of October 18th – 21st, 2009, in Poços de Caldas, Minas Gerais, Brazil. The Organizing Committee of this XV SBQT version was composed by Léo Degrève (USP), Alexandre Braga da Rocha (UFRJ), Munir Salomão Skaf (Unicamp), Paulo Augusto Netz (UFRGS), Regiane de Cássia Maritan Ugulino de Araújo (UFPB), Stella Maris Resende (UFSJR) and Geraldo Magela e Silva (UnB) and we express our gratitude to their efforts in making this an interesting event. The success of this Symposium would be hardly possible without the financial support from many agencies in special, CNPq, CAPES, and the state funding agencies FAPESP (São Paulo), FACEPE (Pernambuco), FAPEMIG (Minas Gerais), FAPERJ (Rio de Janeiro) and FAPDF (Brasilia). Universities over the country provided additional and important support. Finally, we warmly thank the Editorial Assistant Mr. James F. Folks for considerable dedication in handling the online submission and processing the manuscripts submitted for publication. We also thank Prof. Erkki Brändas and Prof. Yngve Öhrn, the Editors–in–Chief of the International Journal of Quantum Chemistry, for their commitment and support for the publication of these proceedings.

MeTA studio: A cross platform, programmable IDE for computational chemist

The development of a cross-platform, programmable integrated development environment (IDE), MeTA Studio, specifically tailored but not restricted to computational chemists working in the area of quantum chemistry with an emphasis on handling large molecules is presented. The IDE consists of a number of modules which include a visualizer and a programming and collaborative framework. The inbuilt viewer assists in visualizing molecules, their scalar fields, manually fragmenting a molecule, and introduces some innovative but simple techniques for handling large molecules. These include a simple Find language and simultaneous multiple camera views of the molecule. Basic tools needed to handle collaborative computing effectively are also included opening up new vistas for sharing ideas and information among computational chemists working on similar problems. MeTA Studio is an integrated programming environment that provides a rich set of application programming interfaces (APIs) which can be used to easily extend its functionality or build new applications as needed by the users. (http://code.google.com/p/metastudio/).

Structure, stability and electronic properties of TiO2 nanostructures

AbstractThe front cover of this issue depicts a view of two types of lepidocrocite‐based cylindrical nanotubes (TiO2, light grey – titanium, red – oxygen). These structures represent examples of a manifold of stable tubular forms of the titania layer modifications anatase and lepidocrocite. These structures were obtained using density‐functional based calculations and characterize the essen‐tial structural features of synthesized titania nanotubes.Andrey Enyashin is a PhD student at the Institute of Solid State Chemistry at the Ural Branch of the Russian Academy of Sciences in Ekaterinburg. He performed this study during a visit at the Institute of Physical Chemistry and Electrochemistry (IPEC) of the TU Dresden together with Gotthard Seifert. Professor Seifert is head of the theory group at the IPEC. His research interests are in the areas of quantum chemistry, cluster physics and computational materials research.

Maple programs for generating efficient FORTRAN code for serial and vectorised machines

We present two packages written in the language of the Maple Computer Algebra system for creating efficient FORTRAN code. The package called Macrofort provides the user with tools for creating optimised FORTRAN code. Through a realistic application, namely the computation of molecular integrals arising in the area of quantum chemistry, we show how Macrofort can generate optimised FORTRAN code for vectorised machines. The second package called Transfor allows the user to efficiently convert Matrix operations, as written in Maple, into Basic Linear Algebra Subroutines (BLAS). These are the essential building-blocks of fast numerical computation in research and industry. BLAS routines are available for serial, vectorised and parallel machines. These tools provide results beyond the capacities of modern-day compilers.

Problems and prospects in the ab initio treatment of pure and defective crystals

Accurate Hartree-Fock LCAO calculations for moderately complex crystalline systems are now feasible; a number of important applications may be envisaged in the areas of material science and technology. Some critical aspects of the corresponding computer schemes are discussed which are of fundamental importance in determining the cost of the computation. Data are provided concerning actual computations which are indicative of the kind of periodic systems that can (or cannot) be treated at present. The result of a perfect-crystal ab initio HF study can be used as an input for treating with the same approximation local-defect problems, by use of suitable embedding techniques. A scheme of this kind is presented, and its computational implications are discussed: due to the intrinsic complexity of this problem, it may be foreseen that the study of defects in crystals will be a typical application of supercomputers in the area of quantum chemistry.

The influence of 4f electrons on chemistry and various spectrometries

The 4f group is the only one of the five transition groups in condensed matter to exhibit a large difference (8 eV) between ionization energy, I, and electron affinity; a spread of the numerous J-levels over 6 –15 eV for q = 2 –12; the parameters of the refined spin-pairing treatment provide similar I for (7 + q) and q electrons; and photo-electron and optical spectra have clarified the better and lesser known areas of quantum chemistry.