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Updates/Corrections to phiFIT 1.2

The following extensions to phiFIT have been implemented since the release of Version 1.0 (June 2006).

• Version 1.1 saw the introduction of the MLR potential allowing for a two-term uLR(r), as a generalization of the MLJ potential energy function.
• In Version 1.2 (April 2007), the MLR potential function form was reformulated, and extended to allow more than two inverse-power terms to be included in the long-range function uLR(r) .
• In Version 1.2 (April 2007), the sign convention for the inverse-power coefficients defining the long-range contribution to the DELR potential was changed to make it consistent with that for the MLR potential.

Updates in betaFIT 2.0

The following extensions to betaFIT have been implemented since the release of Version 1.2 (April 2007). the Name of the code has been changed (from phiFIT) to reflect our changing the name of the exponent coefficient function in the EMO, MLR and DELR potentials from φ(r) to β(r), and hence changing the names of the exponent polynomial expansion coefficients from φi to βi . This was done to avoid confusion when dealing with 2D or 3D potentials for which the exponent coefficient function β(r) could depend on the polar angles θ and φ .

• Use of a radial variable expanded about rref is allowed for the EMO, MLR and DELR potentials.
• The MLR potential form may now:

1. Make use of the second radial variable yq(r), as per Eq.(11) in the new Manual.
2. uLR(r) may now include damping functions, as per Eq.(13).
3. Possible use of the Aubert-Frecon uLR(r) function of Eq.(15) is introduced as an illustration of the flexibility of the MLR form.
4. The exponent coefficient may (optionally) be represented using Pashov's ``spline-pointwise'' approach.

• The damping function used for the DELR potential form is now the incomplete gamma function of Eq.(14).

Updates in betaFIT 2.1

The following extensions to betaFIT have been implemented since the release of Version 2.0 (June 2009).

• For the EMO, MLR and DELR potentials, the ability to have separate exponent polyomial orders for r > re and r < re has been removed, since experience has shown that the introduction of rref and q achieves the same goal without introducing high-order derivative discontinuities at re
• Following the discussion of Ref.[11], damping functions may have either the generalized Douketis-Scoles type form of Eq.(12) or the generalized Tang-Toennies form of Eq.(13), with the user being allowed/required to specify the limiting short-range behaviour of Eq.(14) and the species-dependent scaling factor ρAB.
• The use of the Aubert-Frecon uLR(r) function of Eq.(15) has been extended to allow for treatment of the b 3Πu state of Li2 and for the 3x3 diagonalization required for treating the 1 3Σg+ state of Li2, as in Ref.[12].
• The damping function used for the DELR potential form may now be either the generalized Douketis-Scoles function of Eq.(12) or the generalized Tang-Toennies function of Eq.(13).