1. Hyperfine Interactions in Palladium Foils during Deuterium/Hydrogen Electrochemical Loading
Jinghao He1, Graham K. Hubler1, Eric Bernardo da Silva2, João G.M. Correia3,4, Juliana Schell3, 5, Vittorio Violante6, Izabela Teles de Matos2, Iberê Souza Ribeiro Junior2, Artur Wilson Carbonari2, Moustapha Thioye7, John Gahl8, Michel Zoghby9
1 Sidney Kimmel Institute for Nuclear Renaissance, Dept. of Physics and Astronomy, University of Missouri, USA
2 Instituto de Pesquisas Energéticas e Nucleares, São Paulo University, Brazil
3 Div. PH-UIS, ISOLDE-CERN, Geneva, Switzerland
4 C2TN, Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, University of Lisbon, Portugal
5 Experimentalphysik, Universität des Saarlandes, Germany
6 ENEA, Italian Agency for Energy New Technologies and Sustainable Development, Rome, Italy
7 State University of New York, Stony Brook, USA
8Nuclear Engineering Program, University of Missouri, USA
9 Consultant, Thoiry, France

2. International Collaboration
2. HfO2 activated at Missouri U. Research Reactor (MURR)
1. HfO2 shipped to MURR from Bonn U.
4. Ion-implanted Pd foils provided by ENEA in Italy shipped to CERN
3. Radioactive HfO2 shipped Bonn U. & 181Hf ion-implanted into Pd
5. SKINR, U. Bonn, French, Portuguese, CERN scientists & visiting Post-Docs from Brazil ran experiments 24/7 for 4 weeks at ISOLDE facility at CERN
6. Project will be Masters thesis for student in Brazil at Sao Paulo U.

3. Outline Motivation Perturbed Angular Correlation (PAC) Spectroscopy
Experimental
Sample Preparation: Radiative Hf Activation, Ion Implantation, Thermal Annealing
PAC Measurements during Electrolysis
PAC Results
First-Principles Calculations of Electric Field Gradients
Summary

4. Motivation: Solid-State Environment of Anomalous Heat Effect
Nuclear Active Environment (Storms)
Vacancy Model for LENR (Hagelstein)
MHz RF emissions in electrolysis
What is correlation between the local environment and electromagnetic fields in the PdDx/PdHx ?
Most research is from Top-Down approach where materials are manipulated to try to induce nuclear reactions. While excess heat is sometimes detected, little information is gained on the mechanism of AHE.
This work is a fundamental physics Bottom-Up approach, trying to determine the microscopic environment of Pd and D in the lattice.

5. Perturbed Angular Correlation Method
PAC: Determine electromagnetic moments of the nuclear state or external electromagnetic fields
First γ emission is isotropic
Second γ emission is NOT isotropic
Angular correlation between γ2 and γ1
the coincidence time spectra

6. What PAC can Tell Us? How PAC is analyzed?
EFG and Nuclear Quadrupole Moment
PAC Data Analysis
Nuclear Quadrupole Frequency
[D] concentration in equilibrium:
Static EFG distribution
Q: Nuclear quadrupole momentum
I: Nuclear spin
e: proton charge
[D] concentration in transition process :
Dynamic EFG distribution
Asymmetry Parameters

7. Pd Sample Preparation: 181Hf Activation and Ion Implantation
Pd Samples were cold-rolled and annealed, provided by V. Violante at ENEA
The samples of size 6mmx5mm were spot welded Pt wires before ion implantation
Radioactive 181Hf(181Ta) (produced at MURR) was implanted at 80 keV (HISKP- Bonn) to a dose of 1011 ions/cm2.
Thermal annealing in vacuum at 550 oC for 1 hour to remove defects created during ion implantation.

8. In-situ PAC Measurements during Electrolysis
PAC experiments were performed at the ISOLDE-CERN SSP laboratories.
Highest loading ratios for PdHx and PdDx achieved in electrolysis at CERN were around 90%.

9. PAC Spectra of PdHx and PdDx

10. Fitting Results of PAC Spectra
In annealed Pd, EFG is almost zero.
In α+β region, EFGs are similar for PdHx and PdDx
ɷ0=15 Mrad/s PdHx and PdDx
From α/β boundary to β phases , EFGs for PdDx increase like a step function, while EFGs for PdHx have no significant increase.
In β phases, EFGs in PdDx are higher than those in PdHx
ɷ0=23 Mrad/s PdDx
ɷ0=15 Mrad/s PdHx
The frequency difference may be attributed to lattice distortions. PdDx has a large lattice distortion than PdHx in β phase.
In β phases,

11. Strong Dynamic Hyperfine Interactions in PdDx, not in PdHx
For D/Pd=0.85, strong EFGs were observed in two PAC spectra
ɷ0=1047(6) Mrad/s, η=0.70(2)
ɷ0= 936(5) Mrad/s, η=0.65(1)
No such strong EFGs were observed in PAC spectra for PdHx
The strong EFG in PdDx is most likely related to defects as well as dynamic transition detected by PAC (e.g. diffusion)
PAC Spectra and Fitting for PdD0.85

12. First-Principles Calculations of EFG
WIEN2K Calculations
Linearized Augmented Plane Wave (LAPW) method
2x2x2 FCC lattice with 32 Pd and desired H atoms (e.g., 27 H), 1 Pd atom replaced by Ta
Radius of Muffin Tin spheres for Ta, Pd, H are 1.80, 1.80, 0.60 AU.
Generalized Gradient Approximation (GGA) for the exchange-correlation energy functional
4x4x4 or 8x8x8 k point grids
Strategy
Determine the lattice parameter of PdHx (say a=4.08Å for TaPd31H27)
Create desired structures with or without defects.
Minimize total energy and/or forces to relax atomic positions (in some cases)
Run Self-Consistent Field (SCF) cycle to calculate EFG and other properties.

13. Model: Configuration of PdHx
Perfect Lattice of PdH with one Pd replaced with Ta
Schematic of Shells in FCC PdHx
Difficulty in Modeling in disorder systems:
PAC: average of all EFGs
Both static and Dynamic EFGs H Pd
Pd vacancy
O-site H H
T-site H Ta
What can Ta see?
8 t-sites for H occupancy
6 o-sites for H occupancy
12 Pd atoms with possible Pd vacancies

14. Case I: EFGs in Pure Palladium and PdHx (α+β Phase )
Configuration
Vzz (1021 V/m2) η
ɷp (Mrads/s)
TaPd31 (non-relaxed FCC)
0.0096
0.0859
TaPd30Vac (Vac in 3rd shell)
5.4109
EFG is very small in pure Pd. No EFG was detected for Hf/Ta doped Pd after thermal annealing. PAC would detect EFG if large numbers of vacancies exist.
Note: for 181Hf/181Ta, 1021 V/m2 is equivalent to ɷQ Mrad/s.
Configuration
Vzz (1021 V/m2) η
ɷp (Mrads/s)
TaPd31H5 (no H in 1st shell, relaxed)
EFG in α+β phase has the value close to those from PAC experiments.

15. Case II: EFGs in β Phase (Hydrogen Distribution and Defects)
Configuration
Vzz (1021 V/m2) η
ɷp (Mrads/s)
TaPd31H27 (5H in 1st O-site shell)
TaPd30VacH27 (5H in 1st O-site shell)
TaPd29Vac2H27 (3H in 1st O-site shell)
TaPd31H27 (4H in 1st O-site shell, 1H in 1st T-site shell)
TaPd31H27 (4H in 1st O-site shell, 2H in 1st T-site shell)
Configuration
Vzz (1021 V/m2) η
ɷp (Mrads/s)
TaPd31H27 (3H in 1st O-site shell)
TaPd30VacH27 (3H in 1st O-site shell)
TaPd29Vac2H27 (3H in 1st O-site shell)
TaPd31H27 (2H in 1st O-site shell, 1H in 1st T-site shell)
TaPd31H27 (2H in 1st O-site shell, 2H in 1st T-site shell)
Different hydrogen distribution and existence of vacancy, di-vacancy and tetrahedral site H results in significant increases of EFGs. Dynamic EFG (e.g. H diffusion in the transition process) has not been considered so far.

16. Summary Discovered two major differences in PdHx and PdDx!
No EFGs were detectable in pure Pd after thermal annealing, suggesting defects created in ion implantation of radioactive Hf were recovered.
In α+ β phase, PdDx and PdHx have similar values of nuclear quadrupole frequencies (or EFGs). A step- like increase of nuclear quadrupole frequencies (EFGs) at α/β phase boundary for PdDx, not for PdHx.
In β phase, PdDx has higher nuclear quadrupole frequencies (EFGs) than PdHx, suggesting a large lattice distortion occurs in PdDx.
At D/Pd~0.85, strong EFGs were observed in few PAC spectra for PdDx, not for PdHx. The nuclear quadrupole frequencies can be as high as ~1000 Mrad/s.
EFG calculations were performed using WIEN2k. The calculated EFG of PdHx in α+β phase has the value close to the PAC measurements.
First-principles calculations showed hydrogen distribution in β phase and existence of vacancy and tetrahedral occupancy of hydrogen near the Hf/Ta probes could significantly increase the EFGs. Therefore, the high nuclear quadrupole frequencies in PdDx may be related to a high defect density, especially for the case of 1000 Mrad/s frequency. However, why PdDx (not PdHx) has very strong EFGs is still not fully understood!
Discovered two major differences in PdHx and PdDx!

17. Thank You! Acknowledgements:
The SKINR portion of this work was fully supported by Mr. Sidney Kimmel
The ISOLDE-CERN collaboration 
The FCT-Portugal funding agency through project CERN-FIS-NUC
The Federal Ministry of Education and Research (BMBF) through grants 05K13TSA.
Bonn Isotoper Separator (BONIS) team from Helmholtz-Institut für Strahlen- und Kernphysik (HISKP-Bonn)