Cloud Expansion Coefficient Formula:
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Definition: The Cloud Expansion Coefficient (B) is the Racah interelectronic repulsion parameter that occurs when a transition-metal free ion forms a complex with ligands.
Purpose: It helps quantify the electron-electron repulsion in coordination complexes and is important in understanding their spectroscopic properties.
The calculator uses the formula:
Where:
Explanation: The formula calculates the Racah parameter B from the transition energies observed in the electronic spectrum of a coordination complex.
Details: The B parameter provides information about the strength of the ligand field and the nature of metal-ligand bonding in coordination complexes.
Tips: Enter the three transition energies in Diopter units. All values must be positive numbers.
Q1: What are typical values for B?
A: For transition metal complexes, B typically ranges from 400 to 1200 cm⁻¹ (converted to Diopter as needed).
Q2: How does B relate to ligand field strength?
A: Stronger field ligands generally cause a greater reduction in B compared to the free ion value (nephelauxetic effect).
Q3: What's the difference between B and B₀?
A: B₀ is the Racah parameter for the free ion, while B is the reduced value in the complex due to covalency effects.
Q4: Can this calculator be used for all coordination complexes?
A: It's primarily designed for octahedral d³ and d⁸ complexes where these transitions are observable.
Q5: How accurate is this calculation?
A: It provides a good estimate, but for precise work, more sophisticated calculations may be needed.