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Date of this version of the software:    July 28, 2015

PIPFit version 2015

Ke R. Yang, Zoltan Varga, and Donald G. Truhlar
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA


PIPFit program can be used to fit potential energy surfaces of four-body systems. A weighted least-squares fit is performed with permutationally invariant polynomials (PIPs) of Morse, Gaussian, mixed exponential Gaussian, or hyperbolic secant variables. Three kinds of fit can be performed with the program: PIPs as original proposed by Braams, Bowman, and Xie, modified PIPs by removing the unconnected terms, or modified PIPs by removing the unconnected and the two-body terms. The program can also perform a two-stage fitting scheme in which one fits lower-level energy data at a large number of points and higher-level corrections at a small set.

PIPFit license is available below.

Useful references:

"Global ab initio ground-state potential energy surface of N4" Yuliya Paukku, Ke R. Yang, Zoltan Varga, and Donald G. Truhlar, The Journal of Chemical Physics 139, 044309 (2013); Erratum: 140, 019903 (2014)

"Multi-temperature quasiclassical trajectory analysis of N2 + N2 dissociation reactions using an improved ab initio potential energy surface" Jason D. Bender, Paolo Valentini, Ioannis Nompelis, Yuliya Paukku, Zoltan Varga, Donald G. Truhlar, Thomas Schwartzentruber, and Graham V. Candler, The Journal of Chemical Physics, accepted

PIPFit version 2015 Users Manual:

PDF format

Software Availability:

PIPFit user or group license form
PIPFit site license form
Download PIPFit

Links to Other Pages of Interest:

This document last modified  by Software Manager