Computer Program for Obtaining Restricted Internal Rotational Contributions to the Thermodynamic Functions Calculation of thermodynamic properties of a compound with restricted internal rotation requires the use of tables of the torsional contributions, such as those of Pitser and Gwinn [J. Chern. Phys., 10, 428 (1942)1, which apply t o any molecule that can be regarded ss a rigid frame with attached symmetrical tops. Calculation of the entropy, heat capacity, enthalpy function, and free energy function a t ten temperatures requires one hundred twenty interpolations to obtain the torsional contributions from the tables unless V / R T or I/&, happens to be one of the tabulated values. In order to reduce the amount of work involved, a computer program bas been written in Fortran IV that obtains the contributions of restricted internal rotation for molecules t o which the Pitzer and Gwinn tables apply. Each of the four tables that lists the free energy increase from free rotation, entropy decrease from free rotation, enthalpy, and heat capacity is stored in the program as two three-dimensional arrays, and linear interpolation is used t o find values not listed in the tables. If values a t only the ten temperatures listed in the program are desired, the only input dataare the height of the potential barrier and the reduced moment of inertiaof therotatinggroup. Values of other temperatures must be introduced as input data. The output includes V , I,, snd the five columns, temperature. -(G - G , ) / T , HIT, Si- S, and C,. Program instructions, description, and listing are available from one of the authors (GAC). G. A. CROWDEX PATRICKRILEY' WEST TEXASSTATEUNIVERSITY TEXAS 79015 CANYON,
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