Researchers at Northwestern University and the University of Oxford say that relatively simple methods of explaining chemical bond mechanisms typically taught at undergraduate levels turns out to be an accurate way to understand the arrangement of atoms on a oxide’s surface.

“For a long time we have not understood oxide surfaces,” said Laurence Marks, professor of materials science and engineering in the McCormick School of Engineering and Applied Science at Northwestern. “We only have had relatively simple models constructed from crystal planes of the bulk structure, and these have not enabled us to predict where the atoms should be on a surface.

“Now we have something that seems to work,” Marks said. “It’s the bond-valence-sum method, which has been used for many years to understand bulk materials. The way to understand oxide surfaces turns out to be to look at the bonding patterns and how the atoms are arranged and then to follow this method.”

These findings are published in Nature Materials.

According to a news release, NU graduate student James Enterkin matched the electron diffraction patterns from a strontium titanate surface with the patterns with scanning-tunnelling microscopy images obtained by Bruce Russell at Oxford. Enterkin then combined these with density functional calculations and bond-valence sums, showing that those that had bonding similar to that found in bulk oxides were those with the lowest energy.

Ulrike Diebold, an expert in the investigation of metal oxide surfaces at the Institute of Applied Physics in Vienna, Austria, commented on the significance of this research in a separate article in Nature Materials. She writes, “This simple and intuitive, yet powerful concept [the bond-valence-sum method] is widely used to analyze and predict structures in inorganic chemistry. Its successful description of the surface reconstruction of SrTiO3 (110) shows that this approach could be relevant for similar phenomena in other materials.”

NU provides a fun 3D model of the surface of SrTiO3 (110) here. (Be sure to try to manipulated the model with your mouse.)

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Rueters reported that concentrating solar thermal (CST) company eSolar has reached a deal to license its technology to a Chinese power equipment maker that plans to build a 2,000 megawatt (MW) CST project in China over the next 10 years.

CST uses the sun to heat water, producing steam to power a turbine and create electricity. The technology is seen by some as a viable replacement for fossil-fuel generators because such plants can rival the capacities of many conventional power plants.

The deal comes as the Chinese government aims to boost renewable energy generating capacity in the country, with plans to produce at least 10,000 MW of solar energy and 20,000 MW of wind power by 2020.

“China wants to build on a very large scale. Over time there will be demand for 2 terawatts - two thousand times what we’re making right now,” said eSolar’s founder Bill Gross.

The Pasadena, California-based company has deals with U.S. utilities to create more than 400 megawatts at CST power plants in the Southwest. It recently opened its first commercial power plant in Lancaster, California.

Dan Arvizu, Director of the National Renewable Energy Lab, discusses the role of research and development in the age of renewable energy. Run time 1 hour.

Via press release, Siemens has secured a contract to supply 70 wind turbines to one of Mexico’s largest wind farms, the Los Vergeles project, in a deal that marks its first major turbine order in Latin America.

Grupo Soluciones en Energias Renovables, a Mexican wind-energy developer, will pay Siemens $270 M for the SWT-101 turbines, rated at 2.3 megawatts each. The 160 MW Los Vergeles project will be built in the northeastern Mexican state of Tamaulipas.

“The Latin American wind power market is expected to grow significantly in the years to come,” says Andreas Nauen, chief executive of Siemens’ wind division.

The deal marks the largest order of Siemens’ new 2.3 MW turbine, launched in March 2009. The new turbine, which boasts a swept area of 8,000 square meters, is intended for use in low-wind areas. Siemens claims low-wind areas will soon account for one-third of global turbine sales.