“Under
high pressure, krypton, one of the most inert elements is predicted to become
sufficiently reactive to form a new class of krypton compounds; krypton oxides.
Using modern ab-initio evolutionary algorithms in combination with Density
Functional Theory, we predict the existence of several thermodynamically stable
Kr/O species at elevated pressures.”
Scientists from the
Polish Academy of Sciences Dr. Patrick Zaleski-Ejgierd and Ph.D. student Pawel
M. Lata commenting on their research paper that suggests that Krypton forms
oxides
Chemistry
buffs, the Periodic table has been re-written once more.
Krypton,
the Noble Gas is nobel no more as two scientists from the Physical Chemistry of
the Polish Academy of Sciences (IPC PAS) have presented evidence of oxides of
Krypton as noted in the article “Superman
can start worrying—we've almost got the formula for kryptonite”, published
March 3, 2016, Physorg.
For
a bit of perspective, Krypton in a Group VIII, Period 4 element in the Periodic
Table with an atomic number of 36 (meaning 36 protons) and an atomic mass of
83.798, which is the weight of all its protons and neutrons. It has the
electron configuration [Ar] 3d104s24p6, boils at -153.2 °C and melts at -157.4
°C.
Also,
it was discovered on May 30, 1898 by Scottish chemist Sir William Ramsay and
English chemist Morris M. Travers, while studying liquefied air. So no, this
has nothing to do with superman; it just got that name due its rarity,
constituting only 0.0001% of the atmospheric gases.
These
scientists from the Polish Academy of Sciences,
Dr. Patrick Zaleski-Ejgierd and
Ph.D. student Pawel M. Lata, had cited work in their report in the journal
Scientific Reports that suggested that single linear molecules of Krypton and
Hydrogen and Krypton and Carbon could be forned under high pressure and low
temperatures. This pumps energy into the
stable octet of outer shell electrons and forces the krypton to form bonds, but
only simple molecules.
So
how did the Scientists at the Polish Academy of Sciences achieve this feat?
Polish Academy of
Sciences simulate Krypton Monoxide crystals - How Kyrptonite can be found on
exoplanets
The
scientists have basically discovered two possible compounds of Krypton:
1.
Krypton Tetroxide KrO4
2.
Krypton Monoxide KrO
The
unit cell of krypton monoxide is cuboid with a diamond base, with krypton atoms
at the corners, all bonded covalently as at such high pressures and low
temperatures, covalent bonds are more likely. In the middle of the two opposite
side walls, there is an atom of krypton as shown below.
In
this theoretical unit cell, each atom of oxygen is chemically bound to the two
nearest adjacent atoms of krypton. Long polymer structures are possible and
calculations indicate semiconductor properties for these crystals, which might
be dark or coloured crystals with little light passing through, though not
necessarily glowing green.
Krypton
Tetroxide is a much simpler covalent compound, having a structured similar to
diamond due to it tetrahedral structure. So again, no connection to Superman,
but one can dream!
The
scientists at the Polish Academy of Sciences achieved this by simulating
possible crystalline compounds of krypton using algorithms based on the Density
Functional Theory or DFT for short as described in “Polish
chemists tried to make Kryptonite and failed but then made a huge discovery”,
published March 4, 2016 by Rick Stella, Digitaltrends.
DFT
is a computational quantum mechanical modelling method used in physics,
chemistry and materials science to model electronic configurations of multiple
electron atoms, molecules and condenses phases.
As
an example of the usefulness of DFT, researchers from Ohio State University led
by Dr. Wolfgang Windl had used it to predict that magnetism affects heat and
even sound as explained in my blog article
entitled “How
Ohio State University used DFT to connect Heat, Sound, Radiation and Magnetism”.
By
comparison, Table Salt, as shown in my model here, has a unit cell that has the
shape of a cube, with alternating Sodium and Chloride atoms that are bonded
ionically.
The
simulations suggest massive pressures in the order of 300 to 500 million
atmospheres, to quote Ph.D. student Pawel M. Lata: “Our computer simulations
suggest that crystals of krypton monoxide will be formed at a pressure in the
range of 300 to 500 million atmospheres. This is a high pressure, but it can be
achieved even in today's laboratories, by skillfully squeezing samples in
diamond anvils”.
Still,
those conditions would be very extreme, possibly occurring on exoplanets in the
frigid cold of space as suggested by Polish Academy of Sciences researcher Dr.
Zaleski-Ejgierd, quote: “Reactions occurring at extremely high pressure are
almost unknown, very, very exotic chemistry. We call it 'Chemistry on the
Edge.' Often, the pressures needed to perform syntheses are so gigantic that at
present, there is no point in trying to produce them in laboratories. In those
cases, even methods of theoretic description fail! But what is most interesting
here is the non-intuitiveness. From the very first to the last step of
synthesis you never know what's going to happen”.
Still,
work is still left to be done; another team of scientists can follow on their
work and actually synthesize these crystals, as their semiconductors properties
would be of interest in the development of Quantum computers.
The
noble gas Krypton is noble no more, but at least we can expect to find them
once we develope interstellar travel, visit exoplanets and have the tech to
extract them from their crygonenic sleep!
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