Implications of the virial theorem for quantum-chemical calculations of vibrational frequencies and equilibrium distances

✍ Scribed by Robert G. Parr

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 133 KB
• Volume: 198
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(92)90043-m

✦ Synopsis

Consider two theoretically calculated vibrational potential curves for a specific state of a diatomic molecule, both satisfying the quantum-mechanical virial theorem but the two giving slightly different predictions of equilibrium distance Re and harmonic force constant ke. Let the fractional changes in R~ and ke between the two curves bep and x, and let t and v be the corresponding fractional changes in calculated kinetic and potential energies. Then it is shown that p = t-v and J¢--3t + 4v. A certain model class of molecules gives v= 1.20t, so that x= -9p. For Hartree-Fock H2, t;= 1.17t and ~c= -10.0 p.