Novel states of matter and new chemistry

1. Novel states of matter and new chemistry • Panel chairs: Andrew Cornelius, Dana Dattelbaum • Panelists: • Valentin Iota • YueMeng • ArtemOganov • MaddurySomayazulu • (Choong-shikYoo) • Status: • Identified 3 PRDs • Outlined scientific and technical challenges • High impact topics • Potential Sidebars • HPCAT “want list”

2. From discovery to prediction: new paradigms in extreme condition chemistry • Enormous potential for substantially different (improved) materials • Rich chemistry waiting to be explored with the diamond cell • Foundational understanding of how chemical bonds and electrons behave in extreme conditions HPCAT: Looking Forward • “Throwing periodic table out” – defining new rules at extreme conditions • Unprecedented bonding in “inert” atomic or molecular species • Unusual Xe-halogen extended structures • Stability of hydrogen coordination and hydrogen bond symmetrization • Van der Waals and ionic compounds • “Metallic” behavior • “Holy grail” – metallic hydrogen, > 4 Mbar, (2 Mbar, high temperature) • Superconductivity P/T thresholds, metallic-to-insulator transitions at even high pressures • Polymeric structures – conducting polymers (removing defects), high energy density materials (cg-N, p-CO) • New hydrides (low pressures < 2 GPa, micro-reactors, in-situ reactions) • Ultrahard materials – carbon clusters (b-CN), boron compounds • Shock-driven chemistry – reaction evolution at 20-50 GPa, 2000-4000K, ns timescales

3. HPCAT: Looking Forward From discovery to prediction: new paradigms in extreme condition chemistry Scientific challenges • New definitions of chemical reactivity – define “rules” and exploit them • Prediction of novel structures and properties – integration of theory and experiment to predict phases and their properties • Accessing and diagnosing new phase space with multiple in-situ probes – includes P, T, strain rate, B/e fields, combined static/shock/ramp compression paths • Exploiting metastabilitiesfor synthesis (theory-guided, recovery) • Having the right “probe” at the right state – XRD, spectroscopy, resistivity • Tunability of probes • Design of experiments – conclusively prove/disprove, beyond APS = x-rays, lab = other • What details should be measured to compare to theory? • Robustness of technique with user model (level of development, sophistication) • O(N3) and exponential scaling, limitations on periodicity and # atoms • Cumbersome computations of energy landscapes (potentials/transition states) in extremes, computational limitations on dynamics (ps), roles of excited states

4. In-situ, in real time (smaller, faster): defining the details of chemical transformations in extreme conditions • Chemistry is the study of structure and bonding changes going beyond static properties and stable structures • Major future direction must be time-resolved measurements for following chemical reaction mechanisms and their kinetics in extreme conditions HPCAT: Looking Forward • Competitions between kinetic vs. thermodynamic paths – exploiting potential surfaces, to obtain new products • Time-resolved diffraction techniques using synchrotron pulse sequence and fast detectors focused on structure and bonding changes • Thermal expansion under pulsed laser heating • Phase transformations under intermediate strain rate compression • Phases involved in combustion • Unravel long-standing challenges dynamic compression – pathways through phase diagrams, kinetics in melting/freezing, incomplete transformations/phase hysteresis/retained phases, on-set vs. completion of chemistry • New combinations of dynamic loading paths to reach new phase space– shocking, ramping, fast heating from static states

5. Science Scope-- Fundamental Time Scale 3rd Generation Synchrotron Source APS, Spring8, ESRF 4th Generation Light Source APS upgrade plan Femtosecond Picosecond Nanosecond Microsecond Molecular Vibration Inner-Shell Decay Molecular Rotation Radioactive Decay Solvation Dynamics Energy Transfer in Photosynthesis Electron Transfer in Photosynthesis Non-Thermal Melting & Phase Transitions Spin Dynamics Optical & Acoustic Phonon Thermal Melting Strain Propagation Spatial Resolution 10-9 10-12 10-15 10-6 Sub-micron/Micron Nanometer

6. HPCAT: Looking Forward In-situ, in real time (smaller, faster): defining the details of chemical transformations in extreme conditions Scientific challenges • Kinetic vs. thermodynamic control of reaction pathways and products • Following and interpreting chemical bonding changes in extreme conditions in real-time • Simultaneous probes on sample: XRD, x-ray (ex. XANES) and optical spectroscopies, electronic properties – having the “right” probe, beam sizes, containment of reactive species in DACs • Theory-experiment comparison- limitations on temporal dynamics of simulations – sub-ns • Bridging the “strain rate gap,” and linking static to dynamic processes – new techniques and diagnostics

7. HPCAT: Looking Forward Photon-induced chemical reactions • Photons (optical, x-rays) can drive unique chemical bonding changes due to different selection rules and surmounting activation barriers • Challenge to bring prediction and control to x-ray induced chemistry Mixture of N2/O2(34% N2) • Examples: • Radiation-splitting of H2O – Mao • Using radiation to make new materials – Meng • Explosives decomposition (PETN), generating gases in-situ • “Traditional photochemistry” in extremes 1.5 GPa 0.5 GPa Decomposition Reaction NO2+NO3-, an ionic phase of N2O5 after x-ray radiation of the N2/O2 mixture A know phase previously found Only at low temperatures NO+NO3- at 1.7 GPa after x-ray radiation of NO2+NO3- at 2 GPa for 12 hours A new phase Y. Meng et al, Physical Review B (2006)

8. HPCAT: Looking Forward From discovery to prediction: new paradigms in extreme condition chemistry Scientific challenges • Controlof photo-induced chemical reactions at multiple wavelengths and conditions (P,T) – designing new materials • Means of producing new materials • Multi-wavelength experiments – pump to drive chemistry, x-rays to probe or vice versa • High repetition rate experiments - Laser shock drives, photoactive reactions (outside DACs) • Electron dynamics in extremes (photophysics) – alteration of excited state manifolds under high P/T/strain rate conditions • Avoiding photon-damage – incorporating active filtering at beamlines, knowing what state your sample is in, etc.

9. HPCAT: Looking Forward Overarching Technicalchallenges Beam characteristics • Flux (per pulse), detector technology, data management and analysis • (sub)micron- and variable size beams, improved beam focusing, high resolution energy selectivity • Adapting to diamond cell – better diffraction techniques (reliable intensity information, in situ references, micron control of sample position (incl. off-line) and rotation), single crystals, amorphous scattering • Pulse-to-pulse variation, correct for beam characteristics (intensity, detector efficiency), efficient through-put of pump-probe experiments

10. HPCAT: Looking Forward Overarching Technicalchallenges Sample improvements • Achieving exquisite compositional control, can we redesign sample loading methods, micro-reactors • Larger volumes to higher pressures – necessary for recovery, neutron diffraction, trade-off with time duration?, adapting probes and laser heating for larger volumes (variable laser spot size- unique to HP-CAT) • Mixed phases – probing uniform or non-uniform structures

11. HPCAT: Looking Forward Overarching Technicalchallenges Theory advances • Achieving “linear” scaling – moving to larger atom simulations with enough detail to believe predicted properties/behaviors • Simulating mixed compositions, amorphous/crystalline structures • Predicting synthesis paths – design experiments

12. HPCAT: Looking Forward Sidebar topics • Novel Xe chemistry (Zulu) • Theoretical predictions of novel structures (Oganov) • Radiation-induced chemistry (Meng and Pravica) • Detonation chemistry (Dattelbaum)

13. HPCAT: Looking Forward HP-CAT “want list” – next 10 yrs • “Center concept” with DCS • High priority – theory team (4 pp) providing collaboration and support to users • In-house crystallographer • Should include APS theory/crystallography staff • Diverse expertise- chemistry, materials science, physics • Possible joint positions (between HP-CAT and DCS, APS-external) • Move toward time-resolved measurements: Fast “pumps” for pump-probe – short pulse laser heating, laser-based compression, dynamic DACs, timed to detectors and bunch sequences • Detector development – Pilatus 1M, creative ways of getting multiple frames – multiple CCDs, streaking images (chopper etc.), flux limitations, coordination and scheduling of time-resolved exp’ts due to set-up time • More diagnostics - combinations of “on-line” probes, more off-line capabilities (infrared, absorption, optical pump-probe?), space is an issue – external building(s), walking distance • Sample preparation improvements – glovebox (in process), gas loading - mixtures, micro-machining (laser), micromanipulators, cryogenic loading • Sample and beam alignment – sub-micron beams, precision control, switchable and tunable filters to prevent beam damage, visualization of sample on table, creative ways of getting multiple beams on sample