# FFAST.jl

This is a Julia 1.X implementation of the NIST X-Ray Form Factor, Attenuation, and Scattering Tables (FFAST) database. It is designed to

• only expose data from the NIST FFAST database,
• not depend upon any other physics-related modules,
• not pollute the namespace, and
• impose minimal requirements on the library user.
• Elements are identified by atomic number (Int)
• Shells/edges are identified by index (Int) where 1->K, 2->L1, 3->L2, ...., 25->O9

• Chantler, C.T., Olsen, K., Dragoset, R.A., Chang, J., Kishore, A.R., Kotochigova, S.A., and Zucker, D.S. (2005), X-Ray Form Factor, Attenuation and Scattering Tables (version 2.1). Online Downloaded: 10-Sep-2019. National Institute of Standards and Technology, Gaithersburg, MD.
• Originally published as
• This library is based on tables scraped from the NIST website on 10-Sep-2019.
• The library implements functions to log-log interpolate the tabulated values for
• form factors (f₁ and f₂)
• mass attenuation/absorption coefficients μ/ρ(photoelectric), μ/ρ(coherent/incoherent), μ/ρ(total), μ/ρ(K-only)
• In addition, the library implements functions to access the supplemental values
• mean atomic weight
• edge energies
• nominal density
• relativistic corrections
• nuclear Thompson correction

## Usage

Examples of how to use the major exported methods can be found here.

## Method Documentation

FFAST.EVMethod
EV(::Type{FFASTMAC}, z::Int)::Float64

E(eV) [μ/ρ] in cm²/g = f₂(e/atom) ⋅ EV(::Type{FFASTMAC}, z)

Conversion factor for the f₂ form factor.

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FFAST.densityMethod
density(::Type{FFASTMAC}, z::Int)::Float64

Nominal value of the density of the element in g/cm³.

source
FFAST.eachedgeMethod
eachedge(::Type{FFASTMAC}, z::Int)::Set{Integer}

Returns a set containing the shells for which there is an edge energy in the database for the specified element.

source
FFAST.edgeenergyMethod
edgeenergy(::Type{FFASTMAC}, z::Int, shell::Int)::Float64

The edge energy (in eV) for the specific element and shell. Chantler references these sources for the values

1. Bearden, J.A., Rev. Mod. Phys. 39, 78-124 (1967).
2. Bearden, J.A., Burr, A.F., Rev. Mod. Phys. 39, 125-142 (1967).
source
FFAST.formfactorsMethod
formfactors(z::Int, energy::Float64)::Tuple{Float64,Float64}

Returns a tuple containing the form factors for the specified element and X-ray energy (in eV).

source
FFAST.fractionaluncertaintyMethod
fractionaluncertainty(::Type{FFASTMAC}, ::Type{MonatomicGas}, z::Integer, energy)

Determines from the element and energy, the approximate range of fractional uncertainties to associate with the total and photoelectric components of the mass attenuation coefficients for monatomic gas samples. Based on this table.

source
FFAST.fractionaluncertaintyMethod
fractionaluncertainty(::Type{FFASTMAC}, ::Type{SolidLiquid}, z::Integer, energy)

Determines from the element and energy, the approximate range of fractional uncertainties to associate with the total and photoelectric components of the mass attenuation coefficients for solids and liquids. Based on this table.

source
FFAST.hasedgeMethod
hasedge(::Type{FFASTMAC}, z::Int, shell::Int)::Bool

Is a value available for the specific shell's edge energy for the element identified by atomic number, z.

source
FFAST.jumpratioMethod
jumpratio(::Type{FFASTMAC}, z::Int, shell::Int)::Float64

Returns the jump-ratio for the specified element and shell. This implementation attempts to use the FFAST MAC data to extract the jump-ratio. It uses a simple algorithm in which we look just above and just below the shell edge to determine the height of the edge. Returns zero if the edge isn't available.

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FFAST.macMethod
mac(::Type{FFASTMAC}, ::Type{CoherentIncoherentMAC}, z::Int, energy::Float64)::Float64

Returns the coherent/incoherent attenuation coefficient in cm²/g for the specified element and X-ray energy (in eV).

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FFAST.macMethod
mac(::Type{FFASTMAC}, ::Type{KMAC}, z::Int, energy::Float64)::Float64

Returns the K-shell only attenuation coefficient in cm²/g for the specified element and X-ray energy (in eV).

source
FFAST.macMethod
mac(::Type{FFASTMAC}, ::Type{PhotoElectricMAC}, z::Int, energy::Float64)::Float64

Returns the photoelectric attenuation coefficient in cm²/g for the specified element and X-ray energy (in eV).

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FFAST.macMethod
mac(::Type{FFASTMAC}, ::Type{TotalMAC}, z::Int, energy::Float64)::Float64

Returns the total attenuation coefficient in cm²/g for the specified element and X-ray energy (in eV).

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FFAST.relativisticcorrectionMethod
relativisticcorrection(::Type{FFASTMAC}, z::Int)::Tuple{Float64,Float64}

Relativistic correction estimates fᵣₑₗ(H82,3/5CL) in e/atom. Returns a tuple with two values.

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