Data for: Fast methods of Debye-Hückel limiting slopes calculation and low-temperature extrapolation based on IAPWS equation of state of water

This dataset consists of two parts:
1) Tabulated values for the Debye-Hückel limiting slopes (Aphi, AH/(RT), AC/R, AV, AE, AK) obtained by means of IAPWS equations of state for water. They are stored in .csv files.
2) Software (IAPWS-DH library) that allows to calculate the Debye-Hückel limiting slopes using IAPWS95, IAPWS-IF97 equations. It also supports some other popular equations set (Archer-1990, Bradley&Pitzer-1979). This computer program is written in ANSI C and is cross-platform; at least MS Windows, GNU/Linux and DOS platforms are supported.

The tables were calculated next way:

* At T>=273.15: direct usage of IAPWS95 equation.
* At T<273.15: usage of high-accurate approximation of IAPWS95 equation by means of 2D orthogonal polynomials (to overcome numerical differentiation accuracy problems).

This approach allows to obtain the Debye-Hückel coefficients values for a very low temperature down to about 150 K that can be useful in thermodynamic modelling of very concentrated aqueous solutions using such models as Pitzer, eNRTL or eUNIQUAC models.

本数据集包含两部分内容：
1) 基于国际水和蒸汽性质协会（IAPWS）的水状态方程计算得到的德拜-休克尔极限斜率（Debye-Hückel limiting slopes，即A_φ、A_H/(RT)、A_C/R、A_V、A_E、A_K）的制表数值，相关数据存储于.csv格式文件中。
2) 配套软件（IAPWS-DH库），该工具可基于IAPWS95、IAPWS-IF97状态方程计算德拜-休克尔极限斜率，同时兼容Archer-1990、Bradley&Pitzer-1979等其他主流状态方程集。本程序采用ANSI C语言编写，具备跨平台特性，支持微软Windows、GNU/Linux及DOS操作系统平台。

该数据表的计算方式如下：
* 当温度T≥273.15 K时，直接采用IAPWS95状态方程进行计算；
* 当温度T<273.15 K时，通过二维正交多项式对IAPWS95状态方程进行高精度近似求解，以克服数值微分的精度问题。

该方法可在低至约150 K的极低温区间内获取德拜-休克尔系数数值，可用于基于Pitzer、eNRTL或eUNIQUAC等模型的高浓度水溶液热力学模拟研究。