|
Ammonium dihyrogen phosphate, or ADP, crystals,
which have applications in computer memory, laser and fiber optic
technology.
Photos � by Florida State
University
|
�ADP was discovered in 1938,� Dalal said.
�It was observed to have some unusual electrical properties that
weren�t fully understood - and for nearly 70 years, scientists have
been perplexed by these properties. Using the supercomputer at SCRI (FSU�s
Supercomputer Computations Research Institute), we were able to
perform in-depth computational analyses that explained for the very
first time what causes ADP to have these unusual properties.�
ADP, like many crystals, exhibits an electrical phenomenon known as
ferroelectricity. Ferroelectric materials are analogous to magnets in
that they maintain a positively charged and a negatively charged pole
below a certain temperature that is characteristic for each compound.
�Ferroelectric materials can stay in a given state of charge for a
long time - they retain their charge after the external electrical
source is removed,� Dalal said. �This has made ADP and other materials
like it very useful for storing and transmitting data.
ADP is commonly used in computer memory devices, fiber optic
technology, lasers and other electro-optic applications.�
What researchers found perplexing about ADP was that it often displays
a very different electrical phase - one known as antiferroelectricity.
�With antiferroelectricity, one layer of molecules in a crystal has a
plus and a minus pole, but in the next layer, the charges are reversed,�
Dalal said. �You see this reversal of charges, layer by layer,
throughout the crystal.�
Using the supercomputer at SCRI enabled Dalal and his colleagues to
perform numerous highly complex calculations that couldn�t be
duplicated in a laboratory environment. For example, they were able to
theoretically alter the angles of ADP�s ammonium ions and then measure
the effects on the crystal�s electrical charge. That approach
ultimately led to their solution to the seven-decade mystery.
�We found that the position of the ammonium ions in the compound, as
well as the presence of stresses or defects in the crystal, determine
whether it behaves in a ferroelectric or antiferroelectric manner,�
Dalal said.
The team�s research is important for two main reasons, Dalal said:
�First, this allows us to further understand how to design new
materials with both ferroelectric and antiferroelectric properties.
Doing so could open new doors for computer memory technology - and
possibly play a role in the development of quantum computers.
�Second, our research opens up new ways of testing materials,� Dalal
said. �Using supercomputers, we can quickly perform tests to see how
materials would react under a variety of conditions. Many such tests
can�t even be performed in the lab.�
|
