Angling for gold

A new model provides an alternative description of atomic level gold bonding

2012-09-19

(Press-News.org) A study on how gold atoms bond to other atoms using a model that takes into account bonds direction has been carried out by physicist Marie Backman from the University of Helsinki, Finland, and colleagues. These findings, which are about to be published in EPJ B, are a first step toward better understanding how gold binds to other materials through strong, so-called covalent, bonds.

What scientists need is an empirical model, based on a so-called potential, that describes the gold-gold bond in a reliable way. Most previous models only accounted for interactions in the spherical electron density around the atom. Although it is suitable to describe bonds between gold atom pairs, it is not adequate to describe how surface gold atoms bond to other materials. In such a case, the density of interacting electrons is no longer spherical.

Indeed, bond angles matter when gold binds to other materials. Thus, the authors used a model based on potentials with angular dependence, referred to as Tersoff potential. It offers a compromise between including bond directionality, which is needed for covalent bonds, and keeping the computer time needed for the simulations low.

The authors used theoretical and computational analysis to study gold atoms interacting with their neighbours. They fitted their potential functions to the most important observed characteristics of gold, such as gold atoms' lattice constant, binding energy and elastic constants. Thanks to such potential functions they were then able to describe bonding in atomistic simulations. This involves, first, determining the forces on each atom based on their relative positions and second solving equations of motion, to show how the atoms move, on a very short time scale.

Building on this model, future work could, for example, involve the development of cross potentials for gold nanoparticles and nanorods in a matrix, typically used in biomedical imaging and nanophotonics.

### Reference M. Backman, N. Juslin, and K. Nordlund, Bond order potential for gold, European Physical Journal B 85:317, DOI 10.1140/epjb/e2012-30429-y Image: © Mike Boulden, Caption: "Unravelling gold's bonding mysteries"

For more information, please visit www.epj.org

The full-text article is available to journalists on request.

ELSE PRESS RELEASES FROM THIS DATE:

Barack Obama good for Israel; Barack Hussein Obama less so

2012-09-19

President Obama's middle name, Hussein, makes Israelis – both Jewish and Arab – perceive him as less pro-Israeli, reveals a new study conducted by the University of Haifa and the University of Texas. The study has just been published in the journal Political Behavior. "Even though the Israeli public has extensive information about the American President and his positions, their opinions can still be swayed by cultural cues, such as a name that in this case is perceived as Arabic," says Dr. Israel Waismel-Manor of the University of Haifa who co-authored the study. Similar ...

NEIKER and INRA discover that BDA symptoms in grapevine leaves are a sign of esca

2012-09-19

This press release is available in Spanish.Scientists at the Basque Institute of Agricultural Research and Development, NEIKER-Tecnalia, and the National Institute of Agricultural Research in Bordeaux (INRA) have come to the conclusion that alleged symptoms of 'black dead arm' (BDA) on grapevine leaves are, in fact, those of esca disease in its initial phase. Esca and BDA are diseases that affect the trunk of vines and cause serious losses to the wine-making and grape-growing sectors every year. The symptoms produced by esca and BDA in vine leaves are reminiscent of ...

Preemies' brains reap long-term benefits from Kangaroo Mother Care

2012-09-19

This press release is available in French.Quebec City, September 19, 2012—Kangaroo Mother Care -- a technique in which a breastfed premature infant remains in skin-to-skin contact with the parent's chest rather than being placed in an incubator -- has lasting positive impact on brain development, revealed Université Laval researchers in the October issue of Acta Paediatrica. Very premature infants who benefited from this technique had better brain functioning in adolescence -- comparable to that of adolescents born at term -- than did premature infants placed in incubators. Earlier ...

Stop diabetes with insulin tablets

2012-09-19

Type 1 diabetes is the autoimmune form of diabetes, in which the patients' insulin-producing beta cells are destroyed by their own immune system. "We know that if a person has two autoantibodies and one of them is against insulin, there is a 50 per cent risk that they will develop type 1 diabetes within five years. It doesn't matter how old you are", says Åke Lernmark, Professor of Experimental Diabetes Research at Lund University in Sweden. "There are indications that oral insulin may prevent or delay the clinical onset of type 1 diabetes among individuals with autoantibodies ...

Fighting melanoma's attraction to the brain

2012-09-19

The process of metastasis, by which cancer cells travel from a tumor site and proliferate at other sites in the body, is a serious threat to cancer patients. According to the National Cancer Institute, most recurrences of cancer are metastases rather than "new" cancers. Virtually all types of cancer can spread to other parts of the body, including the brain. Once metastatic melanoma cells are entrenched in the brain, patients typically have only a few months to live. Now Prof. Isaac Witz and his team at Tel Aviv University's Department of Cell Research and Immunology ...

Carbon dioxide from water pollution, as well as air pollution, may adversely impact oceans

2012-09-19

Carbon dioxide (CO2) released into the oceans as a result of water pollution by nutrients — a major source of this greenhouse gas that gets little public attention — is enhancing the unwanted changes in ocean acidity due to atmospheric increases in CO2. The changes may already be impacting commercial fish and shellfish populations, according to new data and model predictions published today in ACS's journal, Environmental Science & Technology. William G. Sunda and Wei-Jun Cai point out that atmospheric levels of CO2, the main greenhouse gas, have increased by about 40 ...

A TECNALIA study reveals the loss of nanomaterials in surface treatments caused by water

2012-09-19

This press release is available in Spanish.Researchers at TECNALIA recently published a study in the prestigious science magazine, Applied Catalysis B: Environmental, which reveals the emission of nanomaterials caused by water runoff on surfaces containing nanomaterials. These surface treatments are employed in numerous consumption and construction products, so evidences of the presence of engineered nanomaterials are beginning to appear in the environment. Concerns about their toxicity for human or the environment rose in the last years, so further studies are required. The ...

Revolutionary ultrathin, flat lens: Smartphones as thin as a credit card?

2012-09-19

Scientists are reporting development of a revolutionary new lens — flat, distortion-free, so small that more than 1,500 would fit across the width of a human hair — capable in the future of replacing lenses in applications ranging from cell phones to cameras to fiber-optic communication systems. The advance, which could lead to smart phones as thin as a credit card, appears in ACS' journal Nano Letters. Federico Capasso and colleagues explain that the lenses used to focus light in eyeglasses, microscopes and other products use the same basic technology dating to the late ...

Toward a better material for hip replacement and other joint implants

2012-09-19

In an advance toward a new generation of improved hip and other joint replacements, scientists are describing development of a potential implant material that flexes more like natural bone, fosters the growth of bone that keeps implants firmly in place and is less likely to fail and require repeat surgery. Their study on these so-called tantalum nanotube materials appears in ACS Applied Material & Interfaces. Hongyi Li, Jinshu Wang and Zhenting Zhang explain that the metal tantalum has advantages over titanium, stainless steel and other metals used in the current generation ...

Selective grazing and aversion to olive and grape leaves achieved in goats and sheep

2012-09-19

Researchers from the Research Group on Ruminants led by Elena Albanell, lecturer in Animal and Food Science at Universitat Autònoma de Barcelona, have successfully achieved to prevent sheep and goats from chewing on the young leaves of olive trees and grapevines when grazing. By using the natural mechanism of conditioned taste aversion, researchers redirected the food preferences of ruminants, making them more willing to eliminate undesirable plants from these types of pastures, and thereby reducing the use of pesticides and farming equipment. The cultivation of woody ...

First-of-its-kind analysis of U.S. national data reveals significant disparities in individual well-being as measured by lifespan, education, and income

Pioneering research reveals some of the world’s least polluting populations are at much greater risk of flooding fuelled by climate change

Reconstruction of historical seasonal influenza patterns and individual lifetime infection histories in humans based on antibody profiles

New study traces impact of COVID-19 pandemic on global movement and evolution of seasonal flu

[Press-News.org] Angling for gold
A new model provides an alternative description of atomic level gold bonding

Angling for gold

ELSE PRESS RELEASES FROM THIS DATE:

LAST 30 PRESS RELEASES: