Testing classical nucleation theory through chemical and isotopic effects on heterogeneous ice nucleation

Testing classical nucleation theory through chemical and isotopic effects on heterogeneous ice nucleation

Quick Decision

Promising with material uncertainties. YES-DTN project YES-27-A-29 is a genuine 2027 PhD project at the University of Leeds, supervised by Thomas Whale and Mark Tarn. It tests whether classical nucleation theory (CNT) explains heterogeneous ice formation by changing solution chemistry and isotopic composition, then comparing freezing behaviour across several atmospheric ice-nucleating materials. The advertised mix of microfluidic and microlitre droplet-freezing experiments, theory and statistical inference is unusually specific, and the Leeds team has directly relevant expertise and facilities. The project is marked non-CASE and non-collaborative, with no project partners. Official project record Whale profile Tarn profile

As checked on 5 November 2026 (Asia/Shanghai), the application opening date is unresolved: the programme’s Join Us page says 10:00 GMT on 2 November 2026, while the detailed application page says 10:00 GMT on 12 November 2026 and says the course code/forms will not be selectable until opening. Both official pages give a closing time of 13:00 GMT on 12 January 2027. Treat the application as status-ambiguous and check the application portal or ask the programme to confirm the opening date; do not treat the opportunity as expired. Join Us dates How To Apply dates and process

The award is a competitive 3.5-year studentship with a stipend at current Research Council rates, tuition and research/training support. International candidates are eligible, within a programme-wide limit of up to 30% of full awards, and award holders’ university tuition is covered regardless of the fee differential. The exact 2027/28 stipend is unpublished. Before investing in a full application, verify the corrected opening date, the funded-versus-registration period, instrument allocation and any bench-fee treatment. Funding and eligibility FAQ Leeds fee table UKRI current rate

Research Problem and Doctoral Work

What Is Unsolved and Why It Matters

Ice nucleation helps determine when supercooled cloud droplets freeze, influencing cloud properties and precipitation. CNT is widely used to interpret nucleation measurements, yet heterogeneous nucleation takes place on chemically and spatially complex surfaces. A few macroscopic parameters may not fully represent surface-specific processes, and similar freezing curves can arise from different microscopic mechanisms. The project’s central question is therefore whether CNT parameters remain physically meaningful when the chemistry, isotopic composition and nucleating material change, or whether those fitted parameters absorb processes outside the theory. Project question Atmospheric ice-nucleation review

Work, Methods, and Potential Outputs

The advertised work spans several material classes: feldspars and other minerals, silver iodide, Snomax, and pollen-derived ice-nucleating macromolecules. The student will vary dissolved-solute identity and concentration, including ions with similar bulk water-activity effects but different interactions with water, ice and nucleating surfaces. Heavy water and H₂O/D₂O mixtures will perturb hydrogen bonding, molecular motion and the thermodynamic driving force for ice formation. Project design

Measurements will combine microfluidic assays with microlitre droplet-freezing assays to cover a broad accessible temperature range. The resulting freezing distributions and nucleation rates will be examined using statistical inference and explicit hypothesis tests. The key comparison is whether consistent, physically interpretable CNT parameters explain responses across materials, droplet sizes, solute conditions and isotopic compositions. Configurational entropy and variation between nucleation sites are possible mechanisms to examine, not predetermined conclusions. Methods and hypotheses Leeds laboratory capability Droplet-freezing statistics

Leeds lists microlitre, microfluidic and infrared NIPI instruments, along with a Raman microscope and IcePod. The facilities appear well matched to the advertised measurement modes. The project page does not specify which instruments will be assigned to the student, and facility availability does not guarantee access to every listed instrument. Clarify the expected assay platform, sample preparation and training plan with the supervisors. Ice Nucleation Laboratory

Potential doctoral contributions include distinguishing material-wide CNT trends from site-specific effects, testing whether similar freezing curves remain consistent under isotopic perturbation, and improving the physical basis for ice-nucleation parameterizations used in cloud and climate models. Those are plausible directions within the advert; no specific result, publication count or model implementation is promised. Advertised scope Field review

School, Programme and Field Context

The degree-awarding host is the University of Leeds, UK, in its School of Earth, Environment and Sustainability. The project is listed under the Atmosphere and Climate theme and is supported by the Institute for Climate and Atmospheric Science (ICAS) environment. ICAS describes a research community using laboratory experiments, field campaigns, satellite analysis and modelling, giving the project a route into broader atmospheric-science questions. Project host and theme Leeds Climate and Atmospheric Science

The School’s REF 2021 submission in Earth Systems and Environmental Sciences (UoA 7) had 96% of research activity assessed as world-leading or internationally excellent; the School reports 95% of outputs and 94% of impact case studies in those bands. The School also reports that Times Higher Education placed it first for “research power,” a measure based on quality and submitted researcher FTE. This is a research-assessment signal from 2021, not a current subject teaching or PhD ranking. School REF 2021 summary

YES-DTN describes cohort training in transferable skills alongside student-led or supervisor-tailored technical training. The University’s standard full-time PhD is normally three years, whereas this award funds 3.5 years. The project page does not say whether registration, stipend duration and any writing-up period align exactly; ask before accepting an offer. YES-DTN research training Leeds research-degree structure

Supervisor and Lab Assessment

Supervisor Research Directions

The official project record names Thomas Whale as primary supervisor and Mark Tarn as academic supervisor. Whale’s work spans experimental and theoretical ice nucleation, crystallisation, atmospheric ice and cryobiology; his profile lists him as Atmospheric Chemistry and Aerosols cluster lead. Tarn’s work combines microfluidics, lab-on-chip, bioaerosol analysis and atmospheric science; his profile notes 18 years of microfluidics device design, fabrication and operation. This gives the project a plausible pairing of physical interpretation and measurement-platform expertise. The project record does not publish meeting cadence or division of day-to-day supervision. Thomas Whale Mark Tarn

Recent Important Publications

• Droplet-freezing statistics (2026): Whale, Surawy-Stepney and Barr adapt survival-analysis methods, including Kaplan–Meier confidence intervals and non-parametric curve comparison, to droplet-freezing data. Their simulations support use across much of the freezing range, while endpoint behaviour and the choice of curve-comparison test remain limitations. This is directly useful for the project’s freezing distributions and hypothesis testing. 2026 survival-analysis paper
• Solute effects (2024): Blow, Whale, Quigley and Sosso examine ammonium substitution in hydrogen-bond networks under realistic surface-charge conditions. Their calculations suggest configurational entropy changes but also show that enthalpic effects influence ion positioning. The work motivates controlled solute comparisons; it does not establish one mechanism for every nucleator. 2024 ammonium-substitution study
• Mechanistic hypothesis (2022): Whale proposes that ammonium disorders hydrogen-bond networks and increases configurational entropy, helping explain enhanced heterogeneous nucleation. The new project broadens this chemical-mechanism question with other ions and isotope perturbations. 2022 ammonium mechanism paper
• Microfluidic measurement (2025): Tarn and colleagues review microfluidics for biological ice-nucleating particles. They describe high droplet throughput and challenges involving sample concentration, rare active particles and integration of sample handling. These are practical questions for the project’s pollen-derived materials. 2025 microfluidics review
• Atmospheric variability (2024): Tarn and colleagues measure mineral and biological contributions to ice-nucleating particles in the eastern Mediterranean. Their field results show that source mix and particle activity vary, reminding readers that laboratory findings from a single material do not automatically generalize to natural aerosol populations. 2024 eastern Mediterranean study
• Pollen variability (2024): Kinney and colleagues test 51 pollen samples from 50 species and report high interspecific variability in ice-nucleation activity. This supports comparing pollen-derived nucleators as a varied class rather than assuming a uniform mechanism. 2024 pollen study

Lab, Resources, and Collaboration Environment

The School’s NIPI suite includes µl-NIPI, microfluidic NIPI and IR-NIPI; droplet sizes allow different parts of the freezing-efficiency and temperature range to be accessed. The School also lists an IcePod and a Raman microscope with a temperature- and humidity-controlled stage. The advert promises the microfluidic and microlitre assay approaches; ask which equipment, sample-characterisation tools and statistical resources this student will actually use. The listing states no CASE project, no collaborative project and no project partners, so do not assume an external industrial placement. Leeds laboratory facilities Project collaboration status

Funding, Application, and Living Cost

The programme overview advertises around 26 PhD studentships each year across its partner schools. The full award covers a stipend at Research Council rates for 3.5 years, university fees, and support for research costs, fieldwork, training and conference travel. The programme FAQ says a 3.75-year award may apply when a student undertakes a three-month industry placement; this project is explicitly non-CASE and no placement is advertised, so the stated base term is 3.5 years. Programme award overview DTP funding terms Project status

UKRI currently lists a 2026/27 minimum stipend of £21,805 and fee level of £5,238. The award’s 2027/28 amount is not published, and the current rate should not be read as a guaranteed future amount. Leeds lists a 2027/28 full-time international PGR fee of £33,000 per year for Earth, Environment and Sustainability; its 2027/28 home fee is still to be confirmed. YES-DTN says it covers university tuition regardless of home/international fee difference for award holders. Leeds notes that high-cost projects may incur an annual bench fee, so ask whether the studentship covers any project-specific bench or consumables charge. UKRI 2026/27 minimum rates Leeds PGR fees International fee coverage

International candidates may receive up to 30% of the programme’s full awards each year. Applicants must meet English requirements and be selected competitively. The award does not cover relocation, travel to the UK, student visa or Immigration Health Surcharge costs; the programme notes that tax may be due in an international student’s home country. Leeds lists IELTS 6.0 overall with at least 5.5 in each component where the requirement applies. International eligibility and exclusions School entry requirements

Leeds estimates average 52-week living costs at £16,640 for a single student in 2026/27, excluding tuition. Its listed budget is indicative, and rent, included bills and personal spending vary. At the current £21,805 stipend reference, the rough balance after the average living-cost estimate is £5,165 before arrival, visa, health-surcharge, flight, setup, tax or rate-change effects. This is a planning comparison, not a promised surplus for October 2027. Leeds 2026/27 living-cost estimate Current stipend reference

The closing deadline is 12 January 2027 at 13:00 GMT on both official programme pages. The application instructions require two submissions: a Leeds Online Application (select “NERC YES DTN Yorkshire Environmental Sciences”) and the YES-DTN JISC form, using project code YES-27-A-29. The programme code is unavailable until applications open; it says a student ID can take up to 48 hours after the Leeds application, so submit well ahead of the deadline. The instructions allow a second-choice project only in the same School and say not to submit a second application. Detailed application instructions Join Us deadline

Applicant Fit and Preparation

Required Background and Skills

The DTP minimum is normally a 2:1 bachelor’s degree or equivalent in a field linked to the project; a good relevant master’s result may support some applicants with a 2:2 first degree. The School likewise asks for a related 2:1 or good performance in a relevant master’s. A first-class degree is usually more competitive for funding. The DTP says it has recruited students changing fields and that demonstrated skills can matter more than exact subject knowledge; it does not require prior publications. The project page lists no named “relevant degree courses,” so the general rules still apply. DTP eligibility School entry requirements Project applicant listing

Applicants should be ready to discuss experimental care, reproducibility, uncertainty and quantitative analysis. Chemistry of aqueous solutions, physical chemistry or physics, materials, atmospheric science, statistics and data handling are likely useful. These are inferred preparation areas from the advertised tasks, not extra formal prerequisites. Relevant examples can come from a dissertation, laboratory project, coding or statistics work, work experience, or a field change that demonstrates transferable methods.

Preferred Experience and Suggested Preparation

No project-specific preferred experience list is published. Before applying, read the 2022/2024 ammonium studies and the 2026 droplet-freezing statistics paper; prepare a concise explanation of what each can and cannot establish. Bring one example showing how you handled noisy data or tested competing explanations, and one example of careful laboratory work. The application guidance says the selection form should contain the requested evidence; sending application materials directly to the supervisor does not count unless requested. Application document instructions Statistical method paper Solute mechanism study

Next Actions and Questions to Verify

Before Applying

1. Ask the programme which opening date is operative. The application page says 12 November and that forms are unavailable until then; the Join Us page says 2 November.
2. Confirm that code YES-27-A-29 remains selectable once the portal opens and whether the 12 January deadline/time applies identically to both forms.
3. Ask the supervisors which assays, instruments and sample classes are certain, whether heavy-water mixtures and all named nucleators are planned within the available budget, and how much time is expected for experiment, theory and quantitative analysis.
4. Confirm the 2027/28 stipend, whether any bench fee applies, and how the award covers the full international tuition fee.

At Interview

1. Which observables would distinguish a change in water activity from changes in surface interactions or configurational entropy?
2. How will microfluidic and microlitre datasets be aligned across temperature ranges, and what role will survival-analysis methods play?
3. How will site-to-site heterogeneity and rare ice-nucleating particles be represented in the statistical tests?
4. What technical training is available for microfluidic device operation, assay reproducibility, coding and theory?

The programme describes three short competency interviews: an academic panel about past research and project skills, plus two panels on transferable attributes. Prepare concise STAR examples, then explain how your research experience relates to this question. Interview preparation

Before Accepting an Offer

1. Is the formal registration period three years or 3.5 years, and how does it relate to stipend end date and any writing-up period?
2. Are relocation, visa, health surcharge, bench fees or extraordinary materials costs covered from any additional fund?
3. What are the supervision cadence, lab access arrangements and facilities available to this specific project?
4. What does the training plan include beyond cohort transferable skills, and are there opportunities for conference travel or a placement despite the non-CASE listing?

Evidence and Sources

Core Project, Programme and School Sources

• S01 — YES-27-A-29 official project record
• S02 — Join Us: studentship overview and dates
• S03 — How To Apply: application steps and dates
• S04 — Funding, international eligibility and selection FAQ
• S05 — Candidate Resources and interviews
• S06 — YES-DTN research training
• S07 — Leeds Climate and Atmospheric Science research area
• S08 — School REF 2021 outcome
• S12 — University of Leeds UK address
• S13 — Leeds research-degree structure

Supervisors, Laboratory and Recent Publications

• S09 — Thomas Whale staff profile
• S10 — Mark Tarn staff profile
• S11 — Ice Nucleation Laboratory facilities
• S22 — 2026 survival analysis for droplet freezing
• S23 — 2024 ammonium substitution study
• S24 — 2022 ammonium disordering mechanism
• S25 — 2025 microfluidics review
• S26 — 2024 eastern Mediterranean ice-nucleating particles
• S27 — 2024 pollen ice-nucleation variability
• S28 — 2023 atmospheric ice-nucleation review

Admissions, Funding, Costs and Careers

• S14 — Leeds School entry requirements
• S15 — Leeds research-degree application guidance
• S16 — Leeds 2027/28 PGR fee table
• S17 — UKRI stipend and fee guidance
• S18 — Leeds living-cost budget
• S19 — YES-DTN career routes and transferable skills
• S20 — National Careers Service climate-scientist profile
• S21 — Met Office science career context