scholarly journals Diffraction of helium on MgO(100) surface calculated from first-principles

2014 ◽  
Vol 16 (39) ◽  
pp. 21106-21113 ◽  
Author(s):  
Ruth Martinez-Casado ◽  
Denis Usvyat ◽  
Giuseppe Mallia ◽  
Lorenzo Maschio ◽  
Silvia Casassa ◽  
...  
Keyword(s):  
Quantum Chemical Calculations ◽  
First Principles ◽  
Quantum Chemical ◽  
Diffraction Peak

In this work we simulate the diffraction peak intensities of He beams scattered on the MgO(100) surface using hierarchical protocol, based on periodic and finite-cluster quantum-chemical calculations.

Theoretical Design of Optical Switches Using the Spin Transition Phenomenon

2006 ◽  
Vol 2 (4) ◽  
pp. 237-249
Author(s):  
Johan Henriksson ◽  
Susanna Nyrell ◽  
Patrick Norman
Keyword(s):  
Quantum Chemical Calculations ◽  
First Principles ◽  
Quantum Chemical ◽  
Optical Switching ◽  
Spin Transition ◽  
Optical Switches ◽  
Transition Phenomenon ◽  
Theoretical Design

The spin characteristics of octahedrically coordinated Fe(II) compounds are determined from first-principles quantum chemical calculations. Four novel Fe(II) spin transition materials are suggested for use in optical switching applications.

Strain manipulation of the local spin flip on Ni@B80 endohedral fullerene

2021 ◽  
Author(s):  
Shuai Xu ◽  
Yiming Zhang ◽  
Rui Huang ◽  
Jing Liu ◽  
Wei Jin ◽  
...  
Keyword(s):  
Quantum Chemical Calculations ◽  
First Principles ◽  
Quantum Chemical ◽  
Endohedral Fullerene ◽  
Local Spin ◽  
Spin Flip ◽  
Highly Correlated

From first principles, we theoretically investigate the strain manipulation of the ultrafast spin-flip processes on the Ni@B80 endohedral fullerene by using highly correlated quantum chemical calculations. It is shown that...

Characterisation of Germanium Monohalides by Solid-State NMR Spectroscopy and First Principles Quantum Chemical Calculations

2013 ◽  
Vol 66 (10) ◽  
pp. 1202 ◽  
Author(s):  
Margaret A. Hanson ◽  
Andreas Schnepf ◽  
Victor V. Terskikh ◽  
Yining Huang ◽  
Kim M. Baines
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Quantum Chemical Calculations ◽  
First Principles ◽  
Solid State Nmr ◽  
Quantum Chemical ◽  
Solid State Nmr Spectroscopy ◽  
Amorphous Nature ◽  
Solid State Structures

Germanium(i) monohalides are useful starting materials to synthesise small, well defined germanium nanoclusters. However, due to the amorphous nature of solid GeBr and GeCl, details of their solid-state structures remain largely unknown. We investigate the arrangement within these novel binary materials using 35Cl, 79Br, and 73Ge solid-state NMR spectroscopy at 21.1 T and first principles quantum chemical calculations in order to suggest a possible model for the structure.

Why Think Up New Molecules?

2012 ◽  
Author(s):  
Roald Hoffmann
Keyword(s):  
Simple Model ◽  
Human Nature ◽  
Quantum Chemical Calculations ◽  
First Principles ◽  
Quantum Chemical ◽  
Model Building ◽  
Microscopic Level ◽  
First Principles Calculations ◽  
Do So

Some theoreticians in chemistry, myself included, like to think about molecules that do not (yet) exist. I use the simple word “think” advisedly, for the design need not use fancy-schmancy computer-intensive “first-principles” calculations. We conjure up the chemical future in so many ways—simple model building, qualitative thinking, and from ever-more-reliable quantum chemical calculations. Even in dreams, as Henning Hopf reminded me, Kekulé’s ouroboric benzene in mind. But why do we try to imagine new molecules? Aren’t there enough molecules already on earth, be they natural or synthetic? A potpourri of reasons follows. Synthesis, the making of molecules, is at the heart of chemistry—the art, craft, business, and science of substances (molecules at the microscopic level) and their transformations. Of course you need to know what substances are, so analysis is a parallel, lively enterprise. As is figuring out why molecules have the colors or other properties they do, why they react in certain ways and not others. Chemists make the objects of their own contemplation. And, of course, study the beautiful evolved world around and within them. By being as much (if not more) in the work of creation as discovery, chemistry is close to art. And lest we get too puffed up on that, creation brings chemistry also close to engineering (which certainly can have artistic elements in it!). I love explaining. But as a theoretician, I also want to take part in the work of creation. I can do so by thinking up interesting molecules not yet made. Maybe, just maybe, an experimentalist will try to make the molecule. Actually, given human nature, a hypothetical molecule will be made more expeditiously if it is thought up by the synthesizer, rather than by me. Since chemistry is a semi-infinite macrocosm of structure, there are many interesting molecules waiting to be made. And still many more that might as well wait a while longer. Few of the 355 dodecanes (C12H26) are extant. For good reasons—new principles, new properties are most unlikely to be found among them. So it’s not just predicting any molecule that does not exist, it’s predicting one that’s in some way “interesting.” That loose word has both cognitive and emotional sides to it, and is definitely subjective. Nevertheless, I find “interesting” works very well, in evoking the psychological mix that makes the intelligent graduate student’s mind hop to.

Electronic, optical and vibrational features of BiVO4 nanostructures investigated by first-principles calculations

RSC Advances ◽  
2016 ◽  
Vol 6 (112) ◽  
pp. 110695-110705 ◽  
Author(s):  
K. Ordon ◽  
A. Kassiba ◽  
M. Makowska-Janusik
Keyword(s):  
Quantum Chemical Calculations ◽  
Surface Reconstruction ◽  
First Principles ◽  
Quantum Chemical ◽  
Numerical Models ◽  
Vibrational Properties ◽  
First Principles Calculations ◽  
Semi Empirical ◽  
Vibrational Features

Numerical models based on DFT and semi-empirical quantum chemical calculations were developed for bulk and nano-sized BiVO4 semiconducting oxide. Importance of surface reconstruction for electronic and vibrational properties was shown.

Discovery of a Difluoroglycine Synthesis Method through Quantum Chemical Calculations

2020 ◽  
Author(s):  
Tsuyoshi Mita ◽  
Yu Harabuchi ◽  
Satoshi Maeda
Keyword(s):  
Quantum Chemical Calculations ◽  
Experimental Verification ◽  
Quantum Chemical ◽  
Synthesis Method ◽  
Target Product ◽  
Systematic Exploration ◽  
Hands On ◽  
Retrosynthetic Analysis ◽  
Synthetic Routes ◽  
Verification Process

The systematic exploration of synthetic pathways to afford a desired product through quantum chemical calculations remains a considerable challenge. In 2013, Maeda et al. introduced ‘quantum chemistry aided retrosynthetic analysis’ (QCaRA), which uses quantum chemical calculations to search systematically for decomposition paths of the target product and propose a synthesis method. However, until now, no new reactions suggested by QCaRA have been reported to lead to experimental discoveries. Using a difluoroglycine derivative as a target, this study investigated the ability of QCaRA to suggest various synthetic paths to the target without relying on previous data or the knowledge and experience of chemists. Furthermore, experimental verification of the seemingly most promising path led to the discovery of a synthesis method for the difluoroglycine derivative. The extent of the hands-on expertise of chemists required during the verification process was also evaluated. These insights are expected to advance the applicability of QCaRA to the discovery of viable experimental synthetic routes.

Discovery of a Difluoroglycine Synthesis Method through Quantum Chemical Calculations

2020 ◽  
Author(s):  
Tsuyoshi Mita ◽  
Yu Harabuchi ◽  
Satoshi Maeda
Keyword(s):  
Quantum Chemical Calculations ◽  
Experimental Verification ◽  
Quantum Chemical ◽  
Synthesis Method ◽  
Target Product ◽  
Systematic Exploration ◽  
Hands On ◽  
Retrosynthetic Analysis ◽  
Synthetic Routes ◽  
Verification Process

The systematic exploration of synthetic pathways to afford a desired product through quantum chemical calculations remains a considerable challenge. In 2013, Maeda et al. introduced ‘quantum chemistry aided retrosynthetic analysis’ (QCaRA), which uses quantum chemical calculations to search systematically for decomposition paths of the target product and propose a synthesis method. However, until now, no new reactions suggested by QCaRA have been reported to lead to experimental discoveries. Using a difluoroglycine derivative as a target, this study investigated the ability of QCaRA to suggest various synthetic paths to the target without relying on previous data or the knowledge and experience of chemists. Furthermore, experimental verification of the seemingly most promising path led to the discovery of a synthesis method for the difluoroglycine derivative. The extent of the hands-on expertise of chemists required during the verification process was also evaluated. These insights are expected to advance the applicability of QCaRA to the discovery of viable experimental synthetic routes.

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