Modeling electron density distributions from X-ray diffraction to derive optical properties: constrained wavefunction...

Area of Science:

• Materials Science
• Crystallography
• Computational Chemistry

Background:

• Designing advanced optical materials requires linking molecular structure to solid-state optical properties.
• X-ray diffraction provides crucial structural data, but electron density alone is insufficient for calculating nonlinear optical properties.
• Multipole refinement has been standard for electron density determination, but has limitations.

Purpose of the Study:

• To compare multipole refinement with X-ray constrained wavefunction refinement for analyzing nonlinear optical materials.
• To assess the reliability of calculating optical properties from experimentally derived wavefunctions.
• To demonstrate the potential of X-ray constrained wavefunction refinement for molecular engineering of optical materials.

Main Methods:

• Applied both multipole refinement and X-ray constrained wavefunction refinement to four molecules with nonlinear optical properties.
• Analyzed electron density distributions and wavefunctions generated by each method.
• Calculated molecular dipole moment, polarizability, hyperpolarizability, and refractive index from experimental wavefunctions.

Main Results:

• Both methods yielded comparable figures of merit and similar electron densities.
• X-ray constrained wavefunction refinement's electron density accuracy depends on nuclear positions.
• Using Hirshfeld atom refinement coordinates improved wavefunction accuracy in the X-ray constrained wavefunction method.
• Experimentally derived optical properties closely matched ab initio calculations.

Conclusions:

• Experimental wavefunctions can be reliably obtained from X-ray diffraction data.
• Optical properties can be accurately calculated from these experimental wavefunctions.
• X-ray constrained wavefunction refinement facilitates the development of custom optical materials.