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New approximations for calculating dispersion coefficients.
Sławomir M Cybulski1, Terence P Haley
1Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
The Journal of Chemical Physics
|October 16, 2004
Summary
New methods improve calculations of dispersion coefficients by scaling time-dependent Hartree-Fock (TDHF) values. These improved approximations for atomic and molecular dispersion coefficients show high accuracy, especially when TDHF results significantly differ from reference values.
Area of Science:
- * Computational Chemistry
- * Quantum Mechanics
- * Theoretical Chemistry
Background:
- * Dispersion coefficients are crucial for describing intermolecular interactions.
- * Accurate calculation of dispersion coefficients is computationally challenging.
- * Time-dependent Hartree-Fock (TDHF) offers a basis but requires refinement.
Purpose of the Study:
- * To develop improved approximation methods for calculating dispersion coefficients.
- * To enhance the accuracy of two-body and three-body isotropic dispersion coefficients.
- * To provide reliable estimations where standard TDHF methods fall short.
Main Methods:
- * Scaling TDHF dispersion coefficients using ratios of static dipole polarizabilities.
- * Utilizing the ratio of estimated true values to TDHF values for scaling factors.
- * Evaluating performance against dipole oscillator strength distribution (DODS) benchmarks.
Main Results:
- * Developed two novel approaches achieving <1.0% average absolute deviation for two-body isotropic dispersion coefficients.
- * Achieved <1.2% average absolute deviation for three-body isotropic dispersion coefficients.
- * Demonstrated superior performance compared to existing methods when TDHF deviates significantly (>10%) from reference values.
Conclusions:
- * Proposed scaling methods offer significant improvements in calculating dispersion coefficients.
- * The new approaches provide highly accurate estimations for both two-body and three-body interactions.
- * These methods are particularly valuable for systems where standard TDHF calculations exhibit large errors.