Software Project Brent Fultz

California Institute of Technology

• Software Functions

• Full Experiment Simulations

• Inversions of Dynamics Models

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

Software Roadmap v. 1.0

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

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

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

Software for Data Acquisition

Within 30 MinutesCalib. FilesOkay ?New RunQuickLookDataS(Q,E)

Within 10 MinutesOkay ?New Run(sample, instrument info.)

QuickLookData

Software for Data Acquisition

DataViewerDetector FilesMark Ω,tInstrumentSimulationSelect ,Q E

Within 2 HoursDiscovery! A feature in the data!Is it magnon, phonon, spurion?

Software for Data Analysis

Before Publication

Relate Data to Dynamics Model

DynamicsModel

Sim. S(Q,E)S(Q,E)DataSim. DataISAW++GraphicsCalc. 4Dfeedbackfeedback

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

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

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

Full Experiment Simulations

Primary Flight Path<kf|H|ki>Secondary Flight PathDetectorSourceSampleSimulationComparisonDataPhysicsModulesSample

ModulesConvergence

Modules

Space

Neutron Wave (or wavepacket)

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

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

EAM Simulations of Phonon DOS from Ni3Al

Large molecular dynamics model. Computationally challenging. Calculated:

PRB 57 (2): 862-869 JAN 1 1998

Scattering Simulations ofLocal Magnetic Dynamics in a Disordered System

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

Result of Inversion — Phonon Partial DOS Curves

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

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!

Fifty initial conditions for Pd3Fe

Try different numbers of nearest neighborsQuality of fit to experimental data

1nn Pd-Pd and Pd-Fe

Pd3Fe force constants from inversions

A case of bad 1nn Pd3Fe force constants

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.

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.

S(Q,E) inversions using coherent scattering

Polycrystalline Ni3Al measured at HFIR with 4 values of Q

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

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!