Featured Research

from universities, journals, and other organizations

Computer Predicts Reactions Between Molecules And Surfaces, With 'Chemical Precision'

Date:
November 9, 2009
Source:
Leiden University
Summary:
An international team of scientists has shown how the chemistry of surface reactions underpinning catalysis can be modeled accurately with computers.

Good news for heterogeneous catalysis and the hydrogen economy: computers can now be used to make accurate predictions of the reactions of (hydrogen) molecules with surfaces. An international team of researchers, headed by Leiden theoretical chemist Geert-Jan Kroes, published on this subject this week in the journal Science.

Related Articles


Hydrogen on copper

The team developed a new method of modelling what happens when hydrogen molecules separate on a copper surface. The way is now open for calculating the interaction between more complex molecules and surfaces.

Kroes: "It's amazing how little we actually know about chemical processes on surfaces. Processes that take place openly and under our very noses." Even the interaction between hydrogen -- with its two atoms, the simplest of all molecules -- and metal surfaces is so complex that it has so far never been possible to describe what happens with quantitative precision.

Yet at the same time the reaction of molecules with surfaces is highly important for society. Their interaction plays a crucial role in heterogeneous catalysis whereby surfaces function as an intermediary allowing two other substances to react with one another. This is what happens with catalysers in cars, for example, and also in the production of the majority of synthetic compounds.

Storage of hydrogen

In the specific case of hydrogen, the interaction between a metal surface and hydrogen molecules also has an important function in the storage of hydrogen, in its turn one of the mainstays in the use of hydrogen as a clean fuel. Separation of hydrogen molecules into two atoms is generally the first step in chemical hydrogen storage methods.

Research into chemical reactions is no longer restricted to the lab; complex computer calculations have become an essential element of this research. Since the sixties, theoreticians have tried to find methods of calculating the forcefield between the atoms of the molecules that are involved in the reactions of molecules with surfaces. The forces between the atoms and therefore the barriers for the activation of energy exert an exponential influence on reaction speed.

The more precise the calculations of the inter-atomic forcefield, the more precise the prediction of the reactions that take place between molecules and surface. However, it is very difficult to calculate the force field, because it calls for an accurate description of two totally different subsystems: that of individual molecules and that of complete metal surfaces.

Chemical precision

Kroes and his team members have now developed a method of making computer models of an important class of molecule-surface reactions, namely the dissociation of hydrogen on a metal surface, with so-called chemical precision.

Kroes: "'Chemical precision' means that we can calculate the energy of the interaction between molecules and surface with a margin of error not greater than 1 kilocalorie per mol. The kilocalorie is the unit of energy familiar to us from diet lists, and a mol is the unit that expresses the number of molecules. There are about 6 x 1023 molecules in one mol. To give you an idea: 1 mol of water weights approximately 18 grams."

The method

To achieve "chemical precision" an advance first had to be made in so-called density function theory (DFT). In this theory, the Hohenberg-Kohn theorems state that the energy of the system (and therefore also the reaction barrier) is determined by the density of the electrons in the system. However, the theory does not explain how exactly the energy is determined from the electron density. The trick that the Leiden researchers applied is to take a so-called functional with a parameter that could be fitted to one experiment on the reaction of 'heavy hydrogen' (D2) with copper. The functional gives the energy as a function of the electron density. Subsequent calculations showed that other experiments on the reaction of H2 on that copper surface could be reproduced accurately using the same functional.

International team

Kroes worked together with former postdoc Cristina Díaz (now at the Universidad Autónoma Madrid), former PhD researcher Ernst Pijper (now working at SARA Reken- en Netwerkdiensten in Amsterdam), Roar Olsen from Oslo, who previously worked at the Vrije Universiteit and at the Theoretical Chemistry department in Leiden, Fabio Busnengo (Universidad Naçional de Rosario, Argentina) and Daniel Auerbach (GRT Inc., Santa Barbara USA). The calculations were made by the Huygens super-computer SARA Reken- en Netwerkdiensten in Amsterdam.

Geert-Jan Kroes has conducted research into molecule-surface reactions for many years, and into the chemistry behind the hydrogen economy.


Story Source:

The above story is based on materials provided by Leiden University. Note: Materials may be edited for content and length.


Journal Reference:

  1. C. Díaz, E. Pijper, R.A. Olsen, H.F. Busnengo, D.J. Auerbach, G.J. Kroes. Chemically Accurate Simulation of a Prototypical Surface Reaction: H2 Dissociation on Cu(111). Science, 2009; 326 (5954): 832 DOI: 10.1126/science.1178722

Cite This Page:

Leiden University. "Computer Predicts Reactions Between Molecules And Surfaces, With 'Chemical Precision'." ScienceDaily. ScienceDaily, 9 November 2009. <www.sciencedaily.com/releases/2009/11/091106102700.htm>.
Leiden University. (2009, November 9). Computer Predicts Reactions Between Molecules And Surfaces, With 'Chemical Precision'. ScienceDaily. Retrieved November 23, 2014 from www.sciencedaily.com/releases/2009/11/091106102700.htm
Leiden University. "Computer Predicts Reactions Between Molecules And Surfaces, With 'Chemical Precision'." ScienceDaily. www.sciencedaily.com/releases/2009/11/091106102700.htm (accessed November 23, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Sunday, November 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

AFP (Nov. 21, 2014) — Toyota presented its hydrogen fuel-cell compact car called "Mirai" to US consumers at the Los Angeles auto show. The car should go on sale in 2015 for around $60.000. It combines stored hydrogen with oxygen to generate its own power. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com
Google Announces Improvements To Balloon-Borne Wi-Fi Project

Google Announces Improvements To Balloon-Borne Wi-Fi Project

Newsy (Nov. 21, 2014) — In a blog post, Google said its balloons have traveled 3 million kilometers since the start of Project Loon. Video provided by Newsy
Powered by NewsLook.com
Raw: Paralyzed Marine Walks With Robotic Braces

Raw: Paralyzed Marine Walks With Robotic Braces

AP (Nov. 21, 2014) — Marine Corps officials say a special operations officer left paralyzed by a sniper's bullet in Afghanistan walked using robotic leg braces in a ceremony to award him a Bronze Star. (Nov. 21) Video provided by AP
Powered by NewsLook.com
British 'Bio-Bus' Is Powered By Human Waste

British 'Bio-Bus' Is Powered By Human Waste

Buzz60 (Nov. 21, 2014) — British company GENeco debuted what its calling the Bio-Bus, a bus fueled entirely by biomethane gas produced from food scraps and sewage. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins