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131.
We have performed a large‐scale evaluation of current computational methods, including conventional small‐molecule force fields; semiempirical, density functional, ab initio electronic structure methods; and current machine learning (ML) techniques to evaluate relative single‐point energies. Using up to 10 local minima geometries across ~700 molecules, each optimized by B3LYP‐D3BJ with single‐point DLPNO‐CCSD(T) triple‐zeta energies, we consider over 6500 single points to compare the correlation between different methods for both relative energies and ordered rankings of minima. We find that the current ML methods have potential and recommend methods at each tier of the accuracy‐time tradeoff, particularly the recent GFN2 semiempirical method, the B97‐3c density functional approximation, and RI‐MP2 for accurate conformer energies. The ANI family of ML methods shows promise, particularly the ANI‐1ccx variant trained in part on coupled‐cluster energies. Multiple methods suggest continued improvements should be expected in both performance and accuracy. 相似文献
132.
Dr. Atef Shalabney Dr. Jino George Dr. Hidefumi Hiura Dr. James A. Hutchison Dr. Cyriaque Genet Prof. Petra Hellwig Prof. Thomas W. Ebbesen 《Angewandte Chemie (International ed. in English)》2015,54(27):7971-7975
Ground‐state molecular vibrations can be hybridized through strong coupling with the vacuum field of a cavity optical mode in the infrared region, leading to the formation of two new coherent vibro‐polariton states. The spontaneous Raman scattering from such hybridized light–matter states was studied, showing that the collective Rabi splitting occurs at the level of a single selected bond. Moreover, the coherent nature of the vibro‐polariton states boosts the Raman scattering cross‐section by two to three orders of magnitude, revealing a new enhancement mechanism as a result of vibrational strong coupling. This observation has fundamental consequences for the understanding of light‐molecule strong coupling and for molecular science. 相似文献
133.
Parks JJ Champagne AR Hutchison GR Flores-Torres S Abruña HD Ralph DC 《Physical review letters》2007,99(2):026601
We study electron transport through C(60) molecules in the Kondo regime using a mechanically controllable break junction. By varying the electrode spacing, we are able to change both the width and the height of the Kondo resonance, indicating modification of the Kondo temperature and the relative strength of coupling to the two electrodes. The linear conductance as a function of T/T(K) agrees with the scaling function expected for the spin-1/2 Kondo problem. We are also able to tune finite-bias Kondo features which appear at the energy of the first C(60) intracage vibrational mode. 相似文献
134.
Jespersen ML Inman CE Kearns GJ Foster EW Hutchison JE 《Journal of the American Chemical Society》2007,129(10):2803-2807
A new method for assembling organic monolayers on gold is reported that employs hafnium ions as linkers between a phosphonate headgroup and the gold surface. Monolayers of octadecylphosphonic acid (ODPA) formed on gold substrates that had been pretreated with hafnium oxychloride are representative of this new class of organic thin films. The monolayers are dense enough to completely block assembly of alkanethiols and resist displacement by alkanethiols. The composition and structure of the monolayers were investigated by contact angle goniometry, XPS, PM-IRRAS, and TOF-SIMS. From these studies, it was determined that this assembly strategy leads to the formation of ODPA monolayers similar in quality to those typically formed on metal oxide substrates. The assembly method allows for the ready generation of patterned surfaces that can be easily prepared by first patterning hafnium on the gold surface followed by alkanephosphonate assembly. Using the bifunctional (thiol-phosphonate) 2-mercaptoethylphosphonic acid (2-MEPA), we show that this new assembly chemistry is compatible with gold-thiol chemistry and use TOF-SIMS to show that the molecule attaches through the phosphonate functionality in the patterned region and through the thiol in the bare gold regions. These results demonstrate the possibility of functionalizing metal substrates with monolayers typically formed on metal oxide surfaces and show that hafnium-gold chemistry is complementary and orthogonal to well-established gold-thiol assembly strategies. 相似文献
135.
Crystallites of Nb4W13O47 were heated by a focussed electron beam in an oxygen atmosphere (pO2 = 20 mbar) inside the gas reaction cell installed within the polepiece of a 400 kilovolt transmission electron microscope. The HRTEM investigation of the resulting oxidation products revealed the presence of structures which differ significantly from those generated by conventional oxidation in air. In a first reaction step, the arrangement of filled pentagonal tunnels in the tetragonal tungsten bronze (TTB) substructure became disordered, and small segregations of ReO3‐type structure arose. Further treatment largely destroyed the original TTB‐type structure. In the residual bronze‐type structure, only a few TTB subcells were preserved while unusual structural arrangements, including hexagonal and heptagonal tunnels, were formed. Moreover, microdomains of a new intergrowth structure between the TTB type and the ReO3 type occur. This structure comprises double pentagons of octahedra as well as slabs of diamond‐linked pentagonal columns. The oxygen excess in the oxidation product is structurally accommodated in large ReO3‐type domains of tungsten oxide. 相似文献
136.
Hutchison W.D. Harker S.J. Chaplin D.H. Funk T. Klein E. 《Hyperfine Interactions》1999,120(1-8):193-198
Combined host (∼95 at% enriched stable 57Fe) and very dilute impurity (∼0.01 at% radioactive 60Co) NMR signals have been obtained on the one sample of polycrystalline Fe foil utilising perturbations to the gamma anisotropy
from in situ thermally oriented 60Co nuclei for both resonances. The NMR-TDNO signals on the 57Fe sites have been followed down to applied magnetic fields well below the host magnetic saturation and exhibited two distinct
components; a strong, narrow homogeneous signal, superimposed over a broader inhomogeneous signal. The impurity 60Co57Fe inhomogeneous resonance has been studied with three pulse NMRON and the irreversible decay of the nuclear spin echo measured
as a function of applied magnetic field.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
137.
Nishimura K. Mori K. Ohya S. Muto S. Hutchison W.D. Harker S.J. Chaplin D.H. 《Hyperfine Interactions》1999,120(1-8):203-207
Low-temperature nuclear orientation was applied to study hyperfine interactions of 142Pr, 147Nd and 143,144Pm nuclei in Pr0.5Nd0.5Ni single crystal. Angular distributions, temperature dependence and external magnetic field effects on the γ-ray anisotropy
are presented. A Nd-Pm exchange interaction seems to dominate the magnetic properties of Pm ions in this system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
138.
Hydrogenic (two-body) systems are the only atomic systems for which uncertainties in calculations of the energy levels approach the current state of the art in frequency measurement. This article discusses progress in the theory and measurement of transition frequencies in hydrogenic systems. These studies have relevance to the determination of fundamental constants and the testing of physical theories, especially quantum electrodynamics. A set of high accuracy calculable frequency standards could also be realized by using hydrogenic systems. 相似文献
139.
R. A. Ganeev D. Y. Lei C. Hutchison T. Witting F. Frank W. A. Okell T. R. Roschuk S. A. Maier J. W. G. Tisch J. P. Marangos 《Applied Physics A: Materials Science & Processing》2013,112(2):457-462
We report the study of extended nanoripple structures formed during the interaction of high-intensity 3.5 fs pulses with a moving silicon wafer. The optimization of laser intensity (8×1013 W?cm?2) and sample moving velocity (1 mm?s?1) allowed the formation of long strips (~5 mm) of homogeneous nanoripples along the whole area of laser ablation. The comparison of nanoripples produced on the silicon surfaces by few- and multi-cycle pulses is presented. We find that few-cycle pulses produce sharp and more homogenous structures than multi-cycle pulses. 相似文献
140.