Ph.D. scholarships in the structure and dynamics of Matter
Application deadline: November 20, 2017
Funded by the VILLUM Foundation for the period 2017-2023 and directed by Prof. Jeppe C. Dyre, Matter is an integrated part of the Glass and Time center (http://glass.ruc.dk) at Roskilde University's Department of Science and Environment. Over the coming years the project will employ a number of Ph.D. students and postdocs.
The purpose of Matter is to determine the range of validity of the isomorph theory for the structure and dynamics of liquids and solids with "hidden scale invariance", see, e.g., J. Phys. Chem. B 118, 10007 (2014) or J. Phys.: Cond. Mat. 28, 323001 (2016).
NB: In the electronic application form's first entry "Description of the project" you are not required to give a detailed project description, but should state which of the six research topics your application relates to and summarize your qualifications for that particular research topic.
We invite applications relating to one of the below six research topics for Ph.D. scholarships beginning January 1, 2018, or soon thereafter. The first two topics are experimental, with support from theory; the next two are simulation projects with support from theory; the final two are theoretical with support from simulations. The deadline for application is November 20, 2017. (for more details, please refer to Matter_scholarships_2017.pdf):
- IA Physical aging
Background: Physical aging is the gradual change of material properties due to adjustments of molecular positions. We have a unique experimental setup for monitoring such processes allowing for fast temperature changes (2 seconds) and extreme temperature stability (±100 µK). Last year we published two aging papers not using isomorph theory. One presented the first algorithm for calculating a non-linear relaxation curve directly from another (Hecksher et al, 2016), one identified theoretically the material time of the Narayanaswamy (1971) aging theory (Dyre, 2015).
- Does the Narayanaswamy theory hold only for R simple systems?
- How to develop a general framework describing the physical aging of R simple systems?
- IB Isomorph jumps
Background: An early prediction (Gnan et al., 2009) was that following a jump between two thermodynamic state points on the same isomorph, the system is instantaneously in equilibrium because the Boltzmann statistical weights are the same for uniformly scaled configurations. As a consequence, jumps between two isomorphs should give identical relaxations, but in-house experiments by Professor Kristine Niss have revealed a more complex picture (Niss, 2017).
- How to develop a theory for jumps controlled via pressure, not density?
- How does this connect to the Narayanaswamy theory of physical aging?
- IIA Coarse-graining
Background: In a paper in preparation we show that even systems with weak virial potential-energy correlations may have isomorph-like curves - "pseudoisomorphs" - along which many, though not all, aspects of structure and dynamics are invariant (Olsen et al., 2016). This shows that the isomorph theory applies even more widely than first anticipated.
- How to systematically identify a coarse-graining leading to pseudoisomorphs?
- Do all systems permit a coarse-graining resulting in lines of invariance for the structure and dynamics of certain degrees of freedom?
- IIB Equations of state and quasiuniversality
Background: The new theory of quasiuniversality (Dyre, 2016) relates to the condensed liquid phase, i.e., to liquid states that are not too far from the melting line - as well as to the entire crystalline phase. There are, however, intriguing recent suggestions of quasiuniversality also for the gas phase, even close to the critical point (Orea et al., 2015).
- Can the isomorph theory be extended to include also the gas phase?
- Is there a quasiuniversal equation of state for R simple systems?
- IIIA 1/d expansion
Background: A few months ago it was shown by Maimbourg and Kurchan (2016) that for atomic systems the isomorph theory is exact in many dimensions. Assuming that this applies also for molecular systems one is led to the following conjecture: R simple systems are those that in three dimensions are "already" like their high-dimensional analogous, i.e., with dominance of first-coordination shell interactions (Ingebrigtsen et al., 2012), whereas for complex systems the transition to simple behaviour takes place in more than three dimensions (Costigliola et al., 2016).
- How to construct a systematic 1/d expansion going from the simple, high-dimensional limit to three dimensions?
- IIIB Quantum systems
Background: The definition of an R simple system refers to a specific property of the potential-energy function. So far we have only studied systems obeying classical mechanics, which is generally believed to describe the motion of matter's atoms or molecules.
- Supposing a quantum system's potential-energy function obeys the R simple condition Eq. (2), which simplifications arise for its genuine quantum properties, e.g., Bose condensation?
- Is there a connection between the isomorph-theory quasiuniversality and that of Ho (2004)?
Costigliola L. et al. (2016), J. Chem. Phys. 144, 231101.
Dyre J. C. (2014), J. Phys. Chem. B 118, 10007.
Dyre J. C. (2015), J. Chem. Phys. 143, 114507.
Dyre J. C. (2016), J. Phys.: Condens. Matter 28, 323001.
Gnan N. et al. (2009), J. Chem. Phys. 131, 234504.
Hecksher T et al. (2015), J. Chem. Phys. 142, 241103.
Ho T.-L. (2004), Phys. Rev. Lett. 92, 090402.
Ingebrigtsen T. et al. (2012), Phys. Rev. X 2, 011011.
Maimbourg T. and J. Kurchan (2016), EPL 114, 6002.
Narayanaswamy O. S. (1971), J. Am. Ceram. Soc. 54, 491.
Niss K. (2017), Phys. Rev. Lett. 119, 115703.
Olsen A. E. et al. (2016), J. Chem. Phys. 145, 231103.
Orea P. et al. (2015), Chem. Phys. Lett. 631, 26.
We are looking for ambitious and open-minded persons with a master's degree in physics or a related field. The successful applicant has also strong mathematics skills and enjoys the close interaction between theory, simulation, and experiment that is emphasized in the Glass and Time center.
For further information you are welcome to contact Prof. Dyre at dyre(at)ruc.dk .
Employment is regulated by an agreement between the Ministry of Finance and the Central Organization of the Academics; thus Ph.D. students have the same rights, formal working hours, vacation, etc., as others in the workforce. After taxes the monthly salary is approximately 16000 DKK (2100 Euro).
Roskilde University welcomes applications from candidates of any social and ethnic backgrounds irrespective of gender, age, religion or any other irrelevant criteria.
Application is submitted via Roskilde University's
Application deadline: November 20, 2017
Research at Glass and Time focuses on understanding the universal physical properties of highly viscous liquids approaching the glass transition. This problem is attacked experimentally as well as by extensive computer simulations in combination with theory; in fact close collaboration and daily interactions between theorists and experimentalists is characteristic feature of the Glass and Time group. Glass and Time consists of several Ph.D. students, postdocs, and experienced scientists. More information about the group can be found at http://glass.ruc.dk