̽��ֱ�� of Cambridge - IBM

AI shows how hydrogen becomes a metal inside giant planets

sc604 — Wed, 09 Sep 2020 15:03:16 +0000

Dense metallic hydrogen – a phase of hydrogen which behaves like an electrical conductor – makes up the interior of giant planets, but it is difficult to study and poorly understood. By combining artificial intelligence and quantum mechanics, researchers have found how hydrogen becomes a metal under the extreme pressure conditions of these planets.

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, IBM Research and EPFL, used machine learning to mimic the interactions between hydrogen atoms in order to overcome the size and timescale limitations of even the most powerful supercomputers. They found that instead of happening as a sudden, or first-order, transition, the hydrogen changes in a smooth and gradual way. ̽��ֱ��results are reported in the journal Nature.

Hydrogen, consisting of one proton and one electron, is both the simplest and the most abundant element in the Universe. It is the dominant component of the interior of the giant planets in our solar system – Jupiter, Saturn, Uranus, and Neptune – as well as exoplanets orbiting other stars.

At the surfaces of giant planets, hydrogen remains a molecular gas. Moving deeper into the interiors of giant planets however, the pressure exceeds millions of standard atmospheres. Under this extreme compression, hydrogen undergoes a phase transition: the covalent bonds inside hydrogen molecules break, and the gas becomes a metal that conducts electricity.

“ ̽��ֱ��existence of metallic hydrogen was theorised a century ago, but what we haven’t known is how this process occurs, due to the difficulties in recreating the extreme pressure conditions of the interior of a giant planet in a laboratory setting, and the enormous complexities of predicting the behaviour of large hydrogen systems,” said lead author Dr Bingqing Cheng from Cambridge’s Cavendish Laboratory.

Experimentalists have attempted to investigate dense hydrogen using a diamond anvil cell, in which two diamonds apply high pressure to a confined sample. Although diamond is the hardest substance on Earth, the device will fail under extreme pressure and high temperatures, especially when in contact with hydrogen, contrary to the claim that a diamond is forever. This makes the experiments both difficult and expensive.

Theoretical studies are also challenging: although the motion of hydrogen atoms can be solved using equations based on quantum mechanics, the computational power needed to calculate the behaviour of systems with more than a few thousand atoms for longer than a few nanoseconds exceeds the capability of the world’s largest and fastest supercomputers.

It is commonly assumed that the transition of dense hydrogen is first-order, which is accompanied by abrupt changes in all physical properties. A common example of a first-order phase transition is boiling liquid water: once the liquid becomes a vapour, its appearance and behaviour completely change despite the fact that the temperature and the pressure remain the same.

In the current theoretical study, Cheng and her colleagues used machine learning to mimic the interactions between hydrogen atoms, in order to overcome limitations of direct quantum mechanical calculations.

“We reached a surprising conclusion and found evidence for a continuous molecular to atomic transition in the dense hydrogen fluid, instead of a first-order one,” said Cheng, who is also a Junior Research Fellow at Trinity College.

̽��ֱ��transition is smooth because the associated ‘critical point’ is hidden. Critical points are ubiquitous in all phase transitions between fluids: all substances that can exist in two phases have critical points. A system with an exposed critical point, such as the one for vapour and liquid water, has clearly distinct phases. However, the dense hydrogen fluid, with the hidden critical point, can transform gradually and continuously between the molecular and the atomic phases. Furthermore, this hidden critical point also induces other unusual phenomena, including density and heat capacity maxima.

̽��ֱ��finding about the continuous transition provides a new way of interpreting the contradicting body of experiments on dense hydrogen. It also implies a smooth transition between insulating and metallic layers in giant gas planets. ̽��ֱ��study would not be possible without combining machine learning, quantum mechanics, and statistical mechanics. Without any doubt, this approach will uncover more physical insights about hydrogen systems in the future. As the next step, the researchers aim to answer the many open questions concerning the solid phase diagram of dense hydrogen.

Reference:
Bingqing Cheng et al. ‘Evidence for supercritical behaviour of high-pressure liquid hydrogen.’ Nature (2020). DOI: 10.1038/s41586-020-2677-y.

Researchers have used a combination of AI and quantum mechanics to reveal how hydrogen gradually turns into a metal in giant planets.

̽��ֱ��existence of metallic hydrogen was theorised a century ago, but what we haven’t known is how this process occurs

Bingqing Cheng

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Unlocking innovation in the supply chain

sc604 — Mon, 25 Apr 2016 23:01:00 +0000

In order to stay innovative, many leading companies run internal programmes, covering a wide range of subjects from technology innovation to business model innovation. But these programmes, in many cases, fail to generate significant value.

Some companies consider collaboration with others in the supply chain. One obvious benefit of doing so would be the integration of capabilities and skills. But it’s almost impossible to integrate different strategies at a large scale, since many companies would be unwilling to share all of their data and information.

Apart from limited innovation, the consequences of locking innovation inside companies are obvious. Knowledge and information are not integrated between companies in the supply chain, so the services and solutions delivered to end customers may not be the best ones. Additionally, supply chains are usually output-focused instead of outcome-focused.

Suppliers seldom focus on the value delivered to end customers. On the other hand, if innovation can’t be unlocked in the supply chain, the supply chain is not efficient. Suppliers, contractors and clients have to discuss back and forth several times before final decisions are made.

In some industries in the UK, such as the utility industry, the regulator has triggered the change to unlock innovation in the supply chain, by directing the industry to be outcome focused and customer focused. Companies are incentivised to explore new models to engage suppliers for innovation. One approach is the formation of a strategic alliance, where suppliers/contractors and the client companies can work together within one organisation, and team up to deliver services and solutions to end customers. Suppliers are contracted on outcomes instead of on outputs, so that they consider the end customers as well as the closest step in the supply chain.

̽��ֱ��shift from output based model to outcome based model and the formation of a strategic alliance to engage suppliers and clients can bring benefits for key stakeholders. For customers, when suppliers are contracted on outcomes and get rewards when customer experience is improved, they will pay attention to end customers, so that customers are expected to get better services. For client companies, in outcome-based contracts, they can transfer some of the responsibilities and related risks to suppliers, and risks and rewards are shared with suppliers. And for suppliers, since they are contracted on outcomes, they will have certain flexibility to choose among possible solutions. In this situation, they are incentivised to innovate and to come up with more efficient and effective solutions.

However, the challenges and barriers are enormous. Partners in the alliance have different business models, and conflicts can arise when they are brought in under the same outcome-based model. Also, partner companies have very diversified backgrounds. Some of them may be competitors outside the strategic alliance, and some of them may not have had smooth relationships previously. If trust and collaboration in the alliance are limited, failure is likely. When the whole industry is still output focused, extended suppliers may have neither the capabilities nor the confidence to be contracted on outcomes. And if the atmosphere in the whole industry is not collaborative, it is challenging to form collaborative and trusting relationships.

We observed this new model closely and worked together with people from industry, aiming to find key points that can ensure the success of an outcome-based model with a strategic alliance approach where suppliers and clients partner with each other to deliver services and solutions to end customers.

In the resulting report, co-authored with IBM, we conclude that there are three areas that partners in the strategic alliance should work on. These three areas are commercial solutions, collaboration and operational design. A commercial solution that is accepted by all partners lays the foundations of working together. Collaboration ensures that partners start to integrate their skills and capabilities, and design and deliver solutions collaboratively. Process design aims to ensure the smooth operation of the strategic alliance.

Commercial Solutions

Since partners are measured against outcomes, a commercial solution should address the risk and reward sharing mechanism and the benefit realisation framework. ̽��ֱ��risk and reward sharing mechanism needs to solve these problems: how benefits and rewards are shared among partners based on contributions, how risks are shared among partners based on accountability, and to what extent the alliance should be measured against end customers’ outcomes. ̽��ֱ��benefit realisation framework needs to solve the following problems: how to decide on the final solutions among many possible capital solutions and operational solutions; how to solve conflicts between return on investments and customer outcomes; and how to solve conflicts among partners regarding their preferences on solutions, etc.

Collaboration

Collaboration should be built from four aspects: strategic objectives, organisational culture, trust and communications. With shared strategic objectives, partners can work towards the same direction. A collaborative and innovative organisational culture needs to be formed within the strategic alliance, collecting the best parts of partners’ organisational cultures. Trust can ensure that partners are willing to share data, knowledge and information, and trust other partners’ decisions. Consistent and efficient communication rules need to be followed, and educational communications will be helpful to deliver the concepts of outcomes and collaboration to every employee.

Operational Design

Operational design includes continuing education, information platforms, process design and metrics and measurements. Continuing education is important to ensure that employees understand the strategic objectives of the alliance and that everyone talks on the same tune. Information platforms help to integrate knowledge and capabilities from partners, and that data and information can flow efficiently. Also, data security needs to be addressed. Process design such as decision-making process, risk management process, culture change process, etc. can facilitate the smooth operations of the alliance. Metrics and measurements that measure the contributions of partners, behaviours of individuals, financial status and the achievements of outcomes also needs paying attention to in everyday operations.

Firms that would like to engage suppliers for innovation can consider forming a strategic alliance, combining suppliers and client companies, while focusing on delivering outcomes to end customers. However, they should be fully aware of the challenges and barriers in this model, and make decisions carefully to ensure success.

Jinchen Hou from the Institute for Manufacturing comments on how members of complex supply chains can form alliances, in order to unlock the innovation that’s often hiding within individual companies.

Nicole Yeary

Ford Rouge Factory Tour

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Farming at nanoscale dimensions

sc604 — Fri, 18 Mar 2016 09:59:33 +0000

Building transistors today is done with lithography, which is a “top-down” process that uses patterning to create the complex layers that make up the transistor structure. It’s a bit like exposing a negative on photographic paper to get the pattern you want and then using this pattern as a template to place each material – metal, insulator or semiconductor – in exactly the right location.

This process has worked successfully since the 1950s, and scientists have even demonstrated the first working test chips with features approaching seven nanometres, the equivalent of placing more than 20 billion tiny switches on chips the size of a fingernail. But as we get to ever-smaller dimensions, new approaches to building nanoscale devices will be required.

At IBM’s T.J. Watson Research Center, and working with researchers from Lund ̽��ֱ�� in Sweden and Stephan Hofmann’s group at the ̽��ֱ�� of Cambridge, we use a technique called self-assembly to grow and directly control nanostructures that could one day form parts of integrated circuits. Self-assembly looks at chip building from the other end of the spectrum: a “bottom-up” approach that builds nanostructures in a way that is dictated by physics rather than by an imposed pattern. In some ways it’s like farming, in that that you plant seeds to grow a crop, and then support the growth with the right conditions to get the result you want.

But exploring self-assembly doesn’t mean we are ready to throw away today’s approach; instead, we want to use top-down strategies that we have already learned over many years, and combine them with new tricks that use self-assembly.

Think of water splashing onto a pane of glass. It spontaneously forms little hemispheres. ̽��ֱ��droplets are hemispherical because surface tension pulls the water molecules into this shape to minimize the surface area and energy of each droplet. But there is no reason for the droplets to form in any particular location or to be any particular size, so their positions and sizes are random. ̽��ֱ��spontaneous formation of the hemispherical shape is an example of self-assembly, but other aspects of the process (position, size) are not controlled.

Now imagine there is a scratch on the glass. Water droplets form on the scratch, because it is a good, low energy place for the water molecules to stick. We have now combined self-assembly – “make a hemispherical droplet on this surface” – with an imposed pattern – “make a droplet on this part of the surface by using carefully placed scratches.” ̽��ֱ��result is that we can build more complicated patterns. Flexible, customised patterns like this water example, but on the nanoscale, help us build integrated circuits.

̽��ֱ��more precisely we can direct this self-assembly, the more versatility we can achieve. We can choose different materials for our nanostructures, build them with different sizes, and control their chemical compositions in ways that allow them to be tuned to have the properties we need. ̽��ֱ��properties of some nanomaterials could include the ability to do the job of a transistor but with less power, or at extreme temperatures beyond what silicon can handle.

How to direct a nanowire

In order to direct self-assembly, we have to understand the physical stimuli that influence atoms to assemble in a certain way as they form a nanostructure. ̽��ֱ��particular nanostructures we find most interesting are called nanowires. These are long thin crystals whose amazing length-to-width ratio could help create very densely packed transistors. Using a combination of imposed patterning and self-assembly, we can grow nanowires spontaneously using the help of catalytic particles. And we can watch the nanowires as they grow, recording the process on video using a one-of-a-kind Ultra High Vacuum Transmission Electron Microscope in our lab.

We load a flat substrate into the microscope, place catalytic particles onto it (this is the directed part of the process), then heat it and add some reactive gases. We watch what happens to the catalytic particles (this is the self-assembly part of the process) by magnifying the image by 50,000 times or more. ̽��ֱ��reaction can be slow – it takes hours for the whole experiment to be finished – but the videos show how the nanostructures grow, one layer of atoms after another. Recording videos, for example at different temperatures or with different added gases, is central to understanding every step of the nanowires’ growth. We get to see cause and effect when the conditions change, so we can work out the laws of physics that control the growth.

Recently, we have become especially interested in growing nanowires made of gallium arsenide that form with the help of catalysts made of gold nanoparticles. For this we need two reactive gases, trimethylgallium and arsine. We chose these because they supply the two components needed to build the nanowire, gallium and arsenic. When we record our movies, the first reaction we see is between gallium and gold. This reaction turns the original gold nanoparticles into hemispherical liquid gold-gallium droplets. As we continue to watch, gallium and arsenic combine within each droplet to start growing a gallium arsenide nanowire beneath the droplet.

Gallium arsenide nanowires grown this way are particularly special because it is possible to change the way the gallium and arsenic atoms stack up within each nanowire. Two arrangements of the atoms are possible, and we can change from one to the other simply by altering the temperature of the reaction or even just varying the ratio of the two gases as they flow past the catalysts. ̽��ֱ��videos show how these changes in growth conditions modify the way the atoms arrange themselves at the junction between the nanowire and the catalyst. And that causes a change in how the atoms eventually stack up when they form the nanowire. We still have the same material, gallium arsenide, but the two possible arrangements of the atoms lead to different electrical properties for the whole nanowire. Understanding what drives atoms to take up one arrangement versus another gives us a better chance of growing nanowires that have the particular electrical properties that are needed for a device such as a nano-transistor. It’s akin to having more colors on your palette so that you can paint a better picture.

These special nanowires, composed of regions with different atomic arrangement, have applications in photonics or single electron transistors, both important building blocks for electronic circuits. And simply knowing that we can control the crystal arrangement in a nanowire will open up the microprocessor community’s imagination for new devices. In particular, optoelectronics, where light and electricity are combined in photonics structures, is a good bet. But that’s just the “tip of the crystal.”

̽��ֱ��latest results of the collaborative work between Cambridge, IBM and Lund ̽��ֱ�� are published in the journal Nature.

Adapted from a blog post by Dr Frances Ross, materials scientist at IBM Research. Originally published on the IBM Research blog.

Reference:
Daniel Jacobsson et. al. 'Interface dynamics and crystal phase switching in GaAs nanowires.' Nature (2016). DOI: 10.1038/nature17148.

Researchers from Cambridge, IBM and Lund ̽��ֱ�� have discovered how tiny 'nanowires' of a widely-used semiconductor self-assemble. Dr Frances Ross of IBM Research explains how the findings could lead to a new crop of nanodevices.

Aidan Sugano

Artistic rendering of self-assembled nanowires composed of different crystal structures that spontaneously grow with the help of a catalytic nanoparticle at the tip of each nanowire.

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New technique to synthesise nanostructured nanowires

sc604 — Thu, 16 Jul 2015 05:00:00 +0000

A new approach to self-assemble and tailor complex structures at the nanoscale, developed by an international collaboration led by the ̽��ֱ�� of Cambridge and IBM, opens opportunities to tailor properties and functionalities of materials for a wide range of semiconductor device applications.

̽��ֱ��researchers have developed a method for growing combinations of different materials in a needle-shaped crystal called a nanowire. Nanowires are small structures, only a few billionths of a metre in diameter. Semiconductors can be grown into nanowires, and the result is a useful building block for electrical, optical, and energy harvesting devices. ̽��ֱ��researchers have found out how to grow smaller crystals within the nanowire, forming a structure like a crystal rod with an embedded array of gems. Details of the new method are published in the journal Nature Materials.

“ ̽��ֱ��key to building functional nanoscale devices is to control materials and their interfaces at the atomic level,” said Dr Stephan Hofmann of the Department of Engineering, one of the paper’s senior authors. “We’ve developed a method of engineering inclusions of different materials so that we can make complex structures in a very precise way.”

Nanowires are often grown through a process called Vapour-Liquid-Solid (VLS) synthesis, where a tiny catalytic droplet is used to seed and feed the nanowire, so that it self-assembles one atomic layer at a time. VLS allows a high degree of control over the resulting nanowire: composition, diameter, growth direction, branching, kinking and crystal structure can be controlled by tuning the self-assembly conditions. As nanowires become better controlled, new applications become possible.

̽��ֱ��technique that Hofmann and his colleagues from Cambridge and IBM developed can be thought of as an expansion of the concept that underlies conventional VLS growth. ̽��ֱ��researchers use the catalytic droplet not only to grow the nanowire, but also to form new materials within it. These tiny crystals form in the liquid, but later attach to the nanowire and then become embedded as the nanowire is grown further. This catalyst mediated docking process can ‘self-optimise’ to create highly perfect interfaces for the embedded crystals.

To unravel the complexities of this process, the research team used two customised electron microscopes, one at IBM’s TJ Watson Research Center and a second at Brookhaven National Laboratory. This allowed them to record high-speed movies of the nanowire growth as it happens atom-by-atom. ̽��ֱ��researchers found that using the catalyst as a ‘mixing bowl’, with the order and amount of each ingredient programmed into a desired recipe, resulted in complex structures consisting of nanowires with embedded nanoscale crystals, or quantum dots, of controlled size and position.

“ ̽��ֱ��technique allows two different materials to be incorporated into the same nanowire, even if the lattice structures of the two crystals don’t perfectly match,” said Hofmann. “It’s a flexible platform that can be used for different technologies.”

Possible applications for this technique range from atomically perfect buried interconnects to single-electron transistors, high-density memories, light emission, semiconductor lasers, and tunnel diodes, along with the capability to engineer three-dimensional device structures.

“This process has enabled us to understand the behaviour of nanoscale materials in unprecedented detail, and that knowledge can now be applied to other processes,” said Hofmann.

Researchers have developed a new method for growing ‘hybrid’ crystals at the nanoscale, in which quantum dots – essentially nanoscale semiconductors – of different materials can be sequentially incorporated into a host nanowire with perfect junctions between the components.

̽��ֱ��key to building functional nanoscale devices is to control materials and their interfaces at the atomic level

Stephan Hofmann

Images recorded in the electron microscope showing the formation of a nickel silicide (NiSi2) nanoparticle (coloured yellow) in a silicon nanowire

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Cambridge Service Alliance

lw355 — Wed, 01 Sep 2010 15:25:29 +0000

̽��ֱ��multinational firms are founding members of the Cambridge Service Alliance – a global partnership between business and academia. ̽��ֱ��Alliance is designed to develop new understanding of 'servitisation', a trend which has seen businesses from a wide range of sectors develop innovative services to meet the changing needs of customers.

In particular, the Alliance will examine complex service solutions which integrate technology, processes, organisations and information in an environment where competition and pressure on public finances ensures the need for ever-increasing effectiveness. These solutions are already being utilised by major organisations such as the British armed forces.

̽��ֱ��new body will investigate how the transition to service can be improved and how it can benefit business. As well as undertaking research into the design and delivery of service excellence, it will develop education programmes and supporting tools and techniques.

Andy Neely, Director of the Cambridge Service Alliance, explains: 'Through-life services can offer customers greater value and reduce costs, while increasing the predictability of future revenue. We’re delighted that BAE Systems and IBM have agreed to be core partners in this new project. Both companies recognise the importance of improving our knowledge of service systems in order to tackle the organisational challenges this brings.'

̽��ֱ��Cambridge Service Alliance builds upon the success of BAE Systems and IBM's previous partnership with the ̽��ֱ�� of Cambridge that investigated new service-related business models. Business-led, the Alliance brings together the Institute for Manufacturing's expertise in the servitisation of high value manufacturing and the Judge Business School's experience in improving business models in a range of industries.

For more information, please contact Rob Halden-Pratt (rwh26@cam.ac.uk), Communications Officer, Institute for Manufacturing.

BAE Systems and IBM have joined forces with the ̽��ֱ�� of Cambridge to launch a new research initiative designed to equip business with the skills needed to deal with complex service systems.

Through-life services can offer customers greater value and reduce costs, while increasing the predictability of future revenue.

Andy Neely

danyrolux from Flickr

Shaking hands

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