### Abstract

We compare the capabilities of the site-site Ornstein-Zernike equation and the Chandler-Silbey-Ladanyi equations to predict the fluid structure for: (i) fluids composed of homonuclear diatomic Lennard‐Jones molecules, and (ii) fluids composed of nonpolar or polar heteronuclear diatomic Lennard‐Jones molecules. In (i), we solve the site-site Ornstein-Zernike (SSOZ) equation with the Percus-Yevick (PY) closure, and the Chandler-Silbey-Ladanyi (CSL) equations with the hypernetted‐chain (HNC) closure to predict the various pair correlation functions at various bond lengths, fluid densities, and temperatures. In general, we find that the CSL equations become more accurate, when compared with computer simulation results, as the bond length increases or as the density decreases, with temperature having no significant effect. In fact, at densities below the critical density, the fluid structure predictions of the CSL equations are found to be in closer agreement with the computer simulation results than those of the SSOZ equation. We also present a general method for computing the low‐order density bridge functions in the context of the CSL equations. In the case of homonuclear diatomic molecules, the zeroth‐order bridge functions, B(0), are found to have little effect on the pair correlation function predictions of the CSL equations. However, the addition of the first‐order bridge functions, B(1), results in a significant improvement of these predictions.
In general, the accuracy of the CSL equations, including the various bridge function corrections, is found to increase as the bond length increases or as the density decreases, similar to what we found when the HNC closure (in which the bridge functions are set equal to zero) was used. Finally, in (ii), we find that for nonpolar heteronuclear diatomic fluids, the CSL equations, with the HNC, HNC+B(0), and HNC+B(1) closures, perform very well in predicting the correlation functions between the larger interactions sites. For polar heteronuclear diatomic fluids, we find that the CSL equations seem to offer an improvement over the SSOZ equation. Once again, the CSL equations provide better predictions for the correlation function between the larger interaction sites. © 1995 American Institute of Physics.

Original language | English |
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Pages (from-to) | 4203-4216 |

Number of pages | 14 |

Journal | Journal of Chemical Physics |

Volume | 102 |

Issue number | 10 |

DOIs | |

Publication status | Published - 8 Mar 1995 |

### Keywords

- interaction site fluids
- extended rism equation
- molecular fluids
- dielectric-constant
- dipolar diatomics
- pair potentials
- liquid-nitrogen
- phase-diagrams
- simulation
- thermodynamics

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## Cite this

Lue, L., & Blankschtein, D. (1995). Application of integral equation theories to predict the structure of diatomic fluids.

*Journal of Chemical Physics*,*102*(10), 4203-4216. https://doi.org/10.1063/1.469468