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Software Project Brent Fultz
California Institute of Technology
• Software Functions
• Full Experiment Simulations
• Inversions of Dynamics Models
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Discussions and Planning Meetings
• Sept. 24, 2001 meeting at Argonne with video to Oak Ridge, McMaster U., Caltech
• Nov. 29, 2001 small meeting at Caltech with postdoc interview.
• March 15, 2002 Software Workshop
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Software Roadmap v. 1.0
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Software Lifetime Exceeds Hardware Lifetime
main (){FILE *fp;/*MEM pair 7/19/89 B. Fultz
This program generates kinetic paths in a binaryalloy with B2 structure.The level of approximation in the kinetic equations isequivalent to the pair (Bethe) approximation in thermodynamics.
Note date above. Code runs just fine,migrated through workstations:austrl, ulysses, hyperfine1, hyperfine2, ARCS
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Software Engineering
Reality: Cannot rewrite all codes in one language such as C++, Java or FORTRAN90
Need New Approach:• Modular software objects connected by object-oriented scripting language
• Different high-level scripts for different experimenters
• Span from detectors to dispersions on common software framework
• Python
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Writing Python Bindings
For example, given a solver routine such as
and a wrapper
double adlib::StableTimeStep();
char pyadlib_stableTimestep__name__[] = “stableTimestep”;PyObject * pyaldib_stableTimestep(PyObject *, PyObject * args){ double dt = adlib::StableTimeStep(“deformation”);
return Py_BuildValue(“d”, dt);}
dt = pyadlib.stableTimestep()
one can place the result of the routine in a python variable
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Software for Data Acquisition
Within 30 MinutesCalib. FilesOkay ?New RunQuickLookDataS(Q,E)
Within 10 MinutesOkay ?New Run(sample, instrument info.)
QuickLookData
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Software for Data Acquisition
DataViewerDetector FilesMark Ω,tInstrumentSimulationSelect ,Q E
Within 2 HoursDiscovery! A feature in the data!Is it magnon, phonon, spurion?
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Software for Data Analysis
Before Publication
Relate Data to Dynamics Model
DynamicsModel
Sim. S(Q,E)S(Q,E)DataSim. DataISAW++GraphicsCalc. 4Dfeedbackfeedback
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Summary: ARCS Software
• Tools Are Required During Data Acquisition Users want software like a smart manservant (to take initiative, but with discretion, and no pay) ARCS needs an engineer to consult on the “user experience”
• Software for Data Analysis Enables New Science:
Full Experiment Simulations (connect to theory)
Analytical Inversions of Data
Single Crystal Data
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S(Q,E) from TOF Data
• Bare minimum for users to take home
• General – model independent
• 3D single crystals, with real-time decisions on sample orientation
• Absolute units [barns, meV, sr, atom, and Å-1]
• Calibration
• Handle resolution and background
• Data visualization
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Working with S(Q,E)
• Visualization
• Comparisons of data sets, arithmetic operations
• Analytical results from the theory of thermal neutron scattering by condensed matter
• Inversions of measured data to obtain force constants or exchange energies.
• Data mining — e.g., recognition of dispersions
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Full Experiment Simulations
Primary Flight Path<kf|H|ki>Secondary Flight PathDetectorSourceSampleSimulationComparisonDataPhysicsModulesSample
ModulesConvergence
Modules
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Space
Neutron Wave (or wavepacket)
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TimeSpacer (t )1 0r (t )1 1r (t )1 2r (t )1 3r (t )1 4r (t )1 5r (t )2 0r (t )3 0r (t )4 0r (t )5 0
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TimeSpacer (t )1 0r (t )1 1r (t )1 2r (t )1 3r (t )1 4r (t )1 5r (t )2 0r (t )3 0r (t )4 0r (t )5 0
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EAM Simulations of Phonon DOS from Ni3Al
Large molecular dynamics model. Computationally challenging. Calculated:
PRB 57 (2): 862-869 JAN 1 1998
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Scattering Simulations ofLocal Magnetic Dynamics in a Disordered System
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Model Inversions — Incoherent Inelastic Scattering from 57Fe
400
300
200
100
0
Cou
nts
6040200-20-40-60
Energy (meV)
3 GPa 12 GPa 17 GPa
• Nuclear resonant scattering of x-rays by 57Fe at APS 3ID
• Pd357Fe in diamond-anvil
cell
• Same analysis as incoherent neutron scattering
• Invert data from 57Fe to obtain full lattice dynamics
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Result of Inversion — Phonon Partial DOS Curves
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Phonon Partial DOS Curves Under Pressure
0.4
0.3
0.2
0.1
0.0
Par
tial D
OS
403020100
Energy (meV)
0 GPa
3 GPa
17 GPa
Fe Pd
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Result of Inversion — Radial 1nn Force Constants vs. Pressure
50
40
30
20
10
0
Rad
ial 1
nn F
orce
Con
stan
t (N
/m)
151050
Pressure (GPa)
Pd-Fe
Pd-Pd
L12 Pd3Fe
Note: Pd-Pd force constants from 57Fe scattering!
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Fifty initial conditions for Pd3Fe
Try different numbers of nearest neighborsQuality of fit to experimental data
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1nn Pd-Pd and Pd-Fe
Pd3Fe force constants from inversions
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A case of bad 1nn Pd3Fe force constants
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Future -- S(Q,E) inversions using coherent scattering
Inversions of incoherent inelastic scattering from 57Fe overcame the neutron-weighting problem in Fe alloys.
More information is available through the Q- or Q-dependence of coherent scattering.
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S(Q,E) inversions using coherent scattering
Polycrystalline Ni3Al measured at HFIR with 4 values of Q(We were looking at order-disorder phenomena...)
Calculated incoherent scattering with Born-von Karman code.
Calculated coherent scattering from all orientations of crystallites w.r.t. Q
Coherent scattering was considered a nuisance to be overcome sowe could produce a phonon DOS.
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S(Q,E) inversions using coherent scattering
Polycrystalline Ni3Al measured at HFIR with 4 values of Q
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S(Q,E) inversions using coherent scattering
Isotropic average of S(Q,E) of polycrystalline Ce, a coherent scatterer.
1.5
1.0
0.5
0.03.02.52.01.51.00.50.0
Frequency (THz)
Q in A-1 3.121 3.335 3.613 3.777
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Summary
• A roadmap exists for the ARCS software project, but it is still subject to change.
• Individual roads are modules connected by Python: S(Q,E) visualization fits to models
full experiment simulation
• Work is underway on phonon dynamics inversions incoherent scattering is useful coherent scattering should be even better
• The year 2002 will be an assessment of existing packages. Please let us know your views!