Volume 9 Issue 9, September 2010

The ramifications of the Car–Parrinello method, a 25-year-old unified approach to computing properties of materials from first principles, have reached out well-beyond materials science.

Nature Materials asked Michele Parrinello about his research and the way in which his work with Roberto Car 25 years ago has influenced the materials science and quantum chemistry communities.

Roberto Car tells Nature Materials how the Car–Parrinello molecular dynamics method originated and how his research career has evolved since then.

A magnetically colour-tunable material is used to create colour-coded microparticles that can be manipulated using magnetic fields and are suitable for use in multiplex bioassays.

A new multiscale computational method that is capable of predicting solute strengthening of alloys without adjustable parameters may lead to the development of new engineering materials.

A conventional material used in magnetic tunnel junctions with in-plane magnetization can also be magnetized perpendicularly, offering new possibilities for high-performance memory and logic circuits.

A liquid/air interface provides an effective platform for organizing thin molecular layers that can be transferred to solid surfaces. It is now shown that liquid-interface assembly is effective for generating extensive membranes of binary nanocrystal superlattices.

Combining optical spectroscopy and transport measurements illuminates the conduction mechanism in high-quality, polycrystalline films.

As the First International Nanotechnology Congress hosted in Quito clearly corroborated, Ecuador is betting on nanotechnology as one of its proposed key investment areas. It is now up to decision-makers to make it happen.

The simplest iron-based superconductor is the chalcogenide Fe_1+yTe_1−xSe_x. Previous work suggested a different magnetic origin of superconductivity owing to differences in its electronic states of this material and the iron pnictides, or at least in their parent compounds —the undoped and non-superconducting versions. The differences are now reconciled by showing a modification of the Fe_1+yTe_1−xSe_x states when the Se content is increased.

Materials with perpendicular anisotropy receive considerable attention owing to their potential in being employed in efficient memory devices. It is now shown that a type of magnetic tunnel junction widely studied for in-plane magnetic anisotropy has all the properties necessary to realize stable and efficient devices based on perpendicular magnetic anisotropy.

Single phosphorus dopants in silicon are one of the physical systems that could be used for quantum information technology. It is now shown that bismuth dopants have similar properties to their phosphorus counterparts, and could offer even more possibilities for quantum information applications.

Terahertz emitters, such as quantum cascade lasers (QCLs), are of interest for applications in imaging and sensing. Nevertheless, performance problems such as power out-coupling efficiency have limited their technological potential. However, a study now shows that subwavelength surface patterning of terahertz QCLs leads to significantly enhanced beam collimation and power collection efficiency.

Measuring charge transport on the surface of an organic semiconductor crystal in field-effect transistors is difficult. Now solution-processed thin films have been used in a field-effect transistor allowing spectroscopic characterization of the carrier over a large temperature range. The measurements provide information on the nonlinear transport properties observed at low temperatures.

Although density functional theory is widely used in surface science, it has a tendency to predict surfaces to be more stable than they actually are experimentally. Using a many-electron approach such as the random-phase approximation enables accurate surface and adsorption energies for carbon monoxide and benzene on metal surfaces to be determined.

Biochemical assays that use magnetic beads are at present in frequent use. Colour-barcoded magnetic microparticles have now been created without using multiple pigmentations. The coding capacity far exceeds that of alternative spectral encoding systems and is demonstrated in a practical bioassay for DNA detection and identification.

The mixing of metals to form alloys with enhanced properties has been known at least since the Bronze Age, although being able to predict their properties remains difficult. An analytical model using computational input is now able to quantitatively predict the mechanical properties of metal yield stress in solute-strengthened alloys.

The control of magnetization by electric fields is important for applications in data storage and sensing. An efficient control of exchange bias by electric fields has now been achieved in thin-film devices in which a ferroelectric antiferromagnet is coupled to a ferromagnet.

The conversion of solar energy into electricity usually occurs either electrically or through thermal conversion. A new mechanism, photon-enhanced thermionic emission, which combines electric as well as thermal conversion mechanisms, is now shown to lead to enhanced conversion efficiencies that potentially could even exceed the theoretical limits of conventional photovoltaic cells.

Structure–property relationships between material properties and stem cell behaviour are investigated using high-throughput methods. The data identify the optimal substrates within a range of different polymeric surfaces to support the growth and self-renewal of human embryonic stem cells from fully dissociated single cells.

After a quarter of a century, it is clear that the Car–Parrinello method has been ground-breaking within the field of computational materials science and has had an enormous impact on fundamental science and applications in a wide range of fields, from solid-state materials physics to chemistry and biology.