How two liquids mix at the surface: an atomic view

Sep 01, 2005
How two liquids mix at the surface: an atomic view

Whenever cream is poured into coffee, these two liquids form a homogeneous mixture, which is difficult to separate again. Other liquids, such as water and oil, do not mix, instead forming emulsions, such as salad dressing.

Image: Schematic representation of atomic-scale demixing observed in BiSn liquid alloy.

In results reported in this week's issue of Physical Review Letters [Phys. Rev. Lett. 95, 106103 (2005)], a collaboration lead by physicists from Harvard University have used x-rays to look at how atoms of two elemental liquids - bismuth and tin - mix together. Despite forming a perfectly miscible alloy in the bulk phase, near the surface the two elements separate into alternating atomic layers.

"The surface demixing is somewhat of a paradox since it occurs due to the strongly enhanced attraction between the atoms of the two components, while for partially miscible mixtures the opposite is true: atoms or molecules are more attracted to their own kind" explains Dr. Oleg Shpyrko, the leading author of the study.

"Surface demixing was predicted in 1950 by Defay and Prigogine, but it eluded experimentalists for more than 50 years: liquids only demix within a nanometer-deep surface region, and there are very few techniques that can probe structure of liquid surfaces on such tiny length scales. As we attempt to understand properties of nanoscale materials where most atoms are near the surface, these and other interfacial effects are expected to play a dominant role."

by Oleg Shpyrko, Argonne National Laboratory
Web address: http://liquids.deas.harvard.edu/oleg/
Email: oshpyrko_AT_anl.gov
Tel: 630-252-7540

Explore further: Physicists design quantum switches which can be activated by single photons

add to favorites email to friend print save as pdf

Related Stories

Meteorites yield clues to Martian early atmosphere

Apr 16, 2014

(Phys.org) —Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published ...

New study outlines 'water world' theory of life's origins

Apr 16, 2014

(Phys.org) —Life took root more than four billion years ago on our nascent Earth, a wetter and harsher place than now, bathed in sizzling ultraviolet rays. What started out as simple cells ultimately transformed ...

JILA's short, flexible, reusable AFM probe

Apr 09, 2014

(Phys.org) —JILA researchers have engineered a short, flexible, reusable probe for the atomic force microscope (AFM) that enables state-of-the-art precision and stability in picoscale force measurements. ...

Building better catalysts for splitting water

Apr 02, 2014

(Phys.org) —The dream of a hydrogen economy—a world run on H2 gas, free from the pollution and politics of fossil fuels—may depend on developing an energy-efficient strategy for splitting water into ...

Recommended for you

Could 'Jedi Putter' be the force golfers need?

Apr 18, 2014

Putting is arguably the most important skill in golf; in fact, it's been described as a game within a game. Now a team of Rice engineering students has devised a training putter that offers golfers audio, ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...