M-CHIPR: A Mathematica program for constructing multi-state coupled adiabatic potential energy functions in triatomic molecule using many body partitioning approach

The permutationally invariant combined hyperbolic inverse power representation (CHIPR) polynomial expansion in terms of hyperbolic secant basis proves to be an efficient model in describing the multi state coupled potential energy surface (MSCPES) and this fact was tested on the O_2H^+ triatomic ion and its diatomic sub units upon dissociation with an unmatchable accuracy of fitting in comparison with the previous works (below 1 cm^-1 in the case of diatomic function and below 300 cm^-1 in the case of triatomic function). In general, this model is capable of modeling A_3 (H_3, O_3 etc.) and ABC (OCS, HCO^+ etc.) triatomic system in addition to the A_2B (O_2H^+) system. This paper presents a Mathematica notebook (M-CHIPR.nb file) to perform the fitting of di and triatomic potentials in a user friendly manner with proper explanations written along side wherever required in the .nb file supplied. The advantage of this code is that the computing clusters are not required to use it and can be run in normal pc with good processor and memory, apart from its numerical accuracy and the system independent consistency over the similar programs written in other languages.

基于双曲正割基的排列不变联合双曲逆幂表示（CHIPR）多项式展开，在描述多态耦合势能面（MSCPES）方面被证明是一种高效的模型。此事实已在O_2H^+ 三原子离子及其二原子子单元在解离过程中的实验中得到验证，与先前的研究相比，其拟合精度无与伦比（在二原子函数的情况下小于1 cm^-1，在三原子函数的情况下小于300 cm^-1）。通常，该模型能够模拟A_3（H_3, O_3等）和ABC（OCS, HCO^+等）三原子系统，以及A_2B（O_2H^+）系统。本文提供了一份Mathematica笔记本（M-CHIPR.nb文件），以用户友好的方式执行二原子和三原子势能的拟合，并在所提供的.nb文件中提供了必要的解释。该代码的优势在于，无需使用计算集群即可运行，且在普通PC上运行，只要处理器和内存性能良好，此外，它还具有数值精度和与其他语言编写的类似程序相比的系统独立一致性。