Spinning around with Spinels – Lithium titanate

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and Structual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and Structual analysis) software http://jp-minerals.org/vesta/en/

Octahedral sites are occupied randomly by lithium (1/6) (not shown in image) and titanium (5/6) atoms. Ti atoms are blue, Li atoms green and O atoms are red.

What is it?

Lithium titanate has a spinel-type structure and is a promising anode candidate for long-life lithium-ion batteries. Current lithium-ion batteries use carbons, such as graphite, but these can feature safety issues when the battery is charged or used rapidly. Li4Ti5O12 is much safer to use at these rapid rates and only features minor structural changes (e.g. expansion/contraction) during battery function. Therefore, it is said to have excellent cyclability andlong term stability at a high capacity.

What makes up a battery?

battery

To the right is a schematic of a coin cell as can be constructed with lithium titanate as an anode material.

A rechargeable battery features chemical reactions that are approximately reversible with charge and use. A lithium-ion battery is rechargeable and relies on the transfer of lithium from the cathode to the anode during charge using electrical current and the reverse during use where it produces electrical current. It is found in many consumer portable electronic devices such mobile phones, computing and entertainment devices.

The lithium-ion battery industry is estimated to be worth $USD11.70 billion in 2012 and is forecast to reach $USD33.11 billion by 2019.

Where did it come from?

Cystallographic information on lithium titanate can be obtained from #4000741 in the open crystallography database.

Resistance is futile – Lanthanum Barium Copper Oxide

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

The Lanthanum Barium Copper Oxide crystal structure, the large green atoms are the mixture of Lanthanum and Barium atoms, with the blue atoms representing copper and the red atoms oxygen.  The copper and oxygen form copper oxide layers (highlighted by the pink sheets) which are critical to the strange properties of this material.

What is it?

While the idea of superconductivity has been around since early last century, the search for a superconducting material that can operate at high temperatures (the so called “High Tc superconductor”) has really only been considered since the 1980s.  This field of research has taken off exponentially since the discovery of the first transition metal oxide, High Tc superconductor, Lanthanum Barium Copper Oxide (La5-x Bax Cu5 O5(3-y), or simply LBCO).  The obvious benefits of room temperature (or higher) superconductors, which conduct electricity without resistance, may include lossless power generators, transformers and transmission lines, powerful supercomputers, and even superfast magnetically levitated trains.  Needless to say, the discovery of room temperature superconductors would revolutionise the way we use and generate power.

Where did the structure come from?

J. Georg Bednorz and K. Alexander Mueller, who were working in the IBM lab at the time, were researching high temperature superconductivity in ceramics when they came across LBCO in 1986. They were able to show that the superconducting transition temperature in this material was 35K – at least 12K higher than the previous superconducting material.  This discovery led to the two scientists sharing the Nobel Prize in Physics in 1987 “for their important break-through in the discovery of superconductivity in ceramic materials”.  Since this discovery there has been a strong race to understand the mechanisms of superconductivity in Cu-O materials, in particular how magnetism influences its behaviour.

The crystal structure displayed here was first reported in Materials Research Bulletin 1985 20 pp667-71.

Certainly not a typical material – the structure of Gadolinium Titanates

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructural analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructural analysis) software http://jp-minerals.org/vesta/en/

What is it?

Certainly this material is not that typical material that you will find in your daily life (except some special people). Why is it so? This is because Gd2TiO5 finds its application as a burnable poison and neutron absorbing material in nuclear reactors. So, unless you are a special person that works in a nuclear reactor, you will not encounter this material on a daily basis.

Gd2TiO5 is used in nuclear reactors as it has good initial neutron absorption capability and irradiation resistance. It plays a role as an additional safety margin, which controls excessive reactivity in the reactor. Recently, researchers have been trying to use Gd2TiO5 for other applications such as memory devices, dielectric sensors, and for my own research, an anode material for sodium-ion batteries. Gd2TiO5 adopts an orthorhombic structure with lots of possible sites that can accommodate the insertions of ions. More importantly, Gd2TiO5seems to be very stable and does not undergo significant volume change during ion insertion.

Where did it come from ?

The structure of Gd2TiO5 is found on the Inorganic Crystal Structure Database (ICSD) # 262620.

Kathleen Lonsdale and her mineral

What does it look like?

Crystal structure of lonsdaleite (hexagonal diamond) by Materialscientist

Crystal structure of lonsdaleite (hexagonal diamond) by Materialscientist

What is it?

Today is the birthday of one of the pioneers of crystallography, Kathleen Lonsdale (1903 to 1971).  Born in Ireland, she studied under WH Bragg at the Royal Institution and determined a number of fundamental structures – including the first determination of a molecular structure, hexamethylbenzene.

She was also very interested in the forms different form carbon and how diamonds could be synthesised, writing this review of the topic in Nature.  As a result, Lonsdaleite, which is another form of carbon discovered in 1967, was named after her.  Otherwise known as hexagonal diamond, Lonsdaleite, is very rare an only found naturally in meteorites.  It can be made in the laboratory, but only by subjecting carbon (in the form of graphite) to extreme high temperatures, and shock pressures – often with explosives.

There has been excitement that Lonsdaleite and a material that is structured (Wurtzite boron nitride) like it, could be tougher than the ‘normal’ diamond.   But although both Lonsdaleite and Wurtzite boron nitride are found naturally and can be made in the lab – we still haven’t made enough of them to test if they are stronger than diamond.  A challenge for future scientists?

Where did the structure come from?

The structure of Lonsdaleite was first reported by Bundy and Kasper in 1967, its structure is available on the American Mineralogical Database.

Fighting the Flu – The structure of Neuraminidase

What is it?

Swine flu, bird flu, and ‘man’ flu. They are all caused by the Influenza virus. The flu virus is continually changing. What we do know is that there are two molecules, hemagglutinin and neuraminidase, that sit on the surface of the virus and are critical for infection. Hemagglutinin is responsible for binding to the cells in our body, so that the virus can then inject its viral genome into our cells. Neuraminidase helps to disengage the virus from our cells. The enzyme clips off the chains that anchor the virus to the cell. By blocking the action of neuraminidase, we can stop viral release and spread, and so it has been an important target for drugs targeting the flu.

What does it look like?

Neuraminidase (pdb code 1nn2: http://www.rcsb.org/pdb/explore.do?structureId=1nn2) is composed of four identical sub-units (green, yellow, pink and blue) packed in a square formation. The enzyme is attached to the surface of the flu virus via a stalk (which is not shown in this picture). Neuraminidase binds to polysaccharide chains and clips off the sugars at the end of these chains, releasing the flu virus from our cells.

Image generated by Pymol (http://www.pymol.org/)

Image generated by Pymol (http://www.pymol.org/)

Where did the structure come from?        

The structure of influenza virus A/Tokyo/3/67 neuraminidase was solved in 1991 by two Australian scientists (Peter Malcolm Colman and Joseph Varghese) (http://www.ncbi.nlm.nih.gov/pubmed/1920428). Since then, many other varieties of flu neuraminidase have been solved, including the swine flu neuraminidase.

Australia’s Role In The War on Flu:

In 1989, scientists at the CSIRO (led by Peter Malcolm Colman and Joseph Varghese) in collaboration with the Victorian College of Pharmacy, Monash University, and Glaxo in the UK, developed the first neuraminidase inhibitor, Zanamivir (marketed as Relenza). Its discovery relied heavily on the availability of the structure of influenza neuraminidase (shown above).

For more information about the discovery of the Relenza drug, see:

M. von Itzstein (2007) The war against influenza: discovery and development of sialidase inhibitors. Nature Reviews Drug Discovery 6, 967-974

A mineral for Australia day – Brucite

What does it look like?

Video by jrrustad on You Tube.

What is it?

It’s Australia day! So while we here are enjoying our BBQ’s on the beach we can introduce you to a mineral called Bruce – Brucite! Apart from the name, it’s not a particularly Australian mineral, the largest deposits of this mineral are found in China and Russia.  Brucite is a layered structure of magnesium hydroxide.  The magnesium atoms in the video are yellow, and are surrounded by six oxygen atoms (which are red).   Each of these oxygen atoms has one hydrogen atom (pink) attached to it, which makes the overall formula of the structure Mg(OH)2. Brucite is used in a number of industries, but most notably it is often used as a fire retardant.  This is because when it is heated it breaks down and releases water.

Where did the structure come from?

This crystal structure of brucite was first determined by G Aminoff in 1921, it can be found in the American mineralogical database.

Buckminsterfullerene a.k.a. Buckyballs a.k.a. C60

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

What is it?

What looks like a soccer ball but has a lot more in common with a diamond? That would be buckminsterfullerene, the carbon structure shown above. With a chemical formula of C60 and a catchy nickname (the bucky-ball) this carbon structure is made up of twenty hexagons and twelve pentagons, which form a truncated icosahedron. Since buckyballs are empty in the middle, they can be used as “atomic shrink wrap”, where a different atom is placed in the center of the C60 cage, which can then be “shrunk” by laser pulses to trap the atom. Like graphite, buckminsterfullerene is a sort mater, however, under pressure it transforms into a superhard structure which can even indent diamonds.

Where did the structure come from?

Buckyballs were first synthesized in the 1980’s by Robert Curl, Harold Kroto, and Richard Smalley. The structure was named after architect Buckminster Fuller, who was well-known for designing geodesic domes. Their work was awarded the 1996 Nobel Prize in Chemistry. The structure is #9011073 on the Crystallography Open Database.