Single crystals of Bis(urea) fumarate (BUF), a urea:fumaric acid co-crystal adduct, were grown from ethanol at 60 °C by the constant-temperature bath method under isothermal slow evaporation conditions, yielding optically homogeneous crystals of 10 × 3 × 3 mm3. Single-crystal XRD confirmed a monoclinic P21/c structure with lattice parameters a = 5.540 Å , b = 8.227 Å , c = 12.426 Å, β = 97.240°, and V = 562 Å3; powder XRD and CHNO analysis verified phase purity and elemental composition. FTIR bands at 3473–3296 cm−1 confirmed N–H···O and O–H···O hydrogen bonding, corroborated by Hirshfeld surface analysis (H···O: 48.2%; H···H: 27.3%). Optical transmittance exceeded 70% over 400–1200 nm with a direct bandgap of 4.81 eV; the laser-induced damage threshold was 4.6 GW cm−2 at 1064 nm. The crystal was thermally stable to 200 °C, showed ductile mechanical behavior (work-hardening coefficient n = 4.2), and exhibited frequency-dependent decrease in dielectric constant and loss. Z-scan measurements at 632.8 nm yielded <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${n}_{2}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>n</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> = 7.583 × 10−8 m2/W, <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\beta$</EquationSource> <EquationSource Format="MATHML"><math> <mi>β</mi> </math></EquationSource> </InlineEquation> = 0.845 × 10−4 m/W, <InlineEquation ID="IEq4"> <EquationSource Format="TEX">${\chi }^{3}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi>χ</mi> </mrow> <mn>3</mn> </msup> </math></EquationSource> </InlineEquation> = 4.172 × 10−6 esu, and <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\gamma$</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation> = 2.336 × 10−27 esu, with an optical limiting threshold of 15 mW at 532 nm.

Crystal Growth, Optical, Mechanical, and Hirshfeld surface analysis of Third-order nonlinear optical single crystal: Bis(urea) Fumarate

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2026年7月3日

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A. Senthil,
T. Bharanidharan,
M. Vennila

摘要

Single crystals of Bis(urea) fumarate (BUF), a urea:fumaric acid co-crystal adduct, were grown from ethanol at 60 °C by the constant-temperature bath method under isothermal slow evaporation conditions, yielding optically homogeneous crystals of 10 × 3 × 3 mm³. Single-crystal XRD confirmed a monoclinic P2₁/c structure with lattice parameters a = 5.540 Å , b = 8.227 Å , c = 12.426 Å, β = 97.240°, and V = 562 Å³; powder XRD and CHNO analysis verified phase purity and elemental composition. FTIR bands at 3473–3296 cm⁻¹ confirmed N–H···O and O–H···O hydrogen bonding, corroborated by Hirshfeld surface analysis (H···O: 48.2%; H···H: 27.3%). Optical transmittance exceeded 70% over 400–1200 nm with a direct bandgap of 4.81 eV; the laser-induced damage threshold was 4.6 GW cm⁻² at 1064 nm. The crystal was thermally stable to 200 °C, showed ductile mechanical behavior (work-hardening coefficient n = 4.2), and exhibited frequency-dependent decrease in dielectric constant and loss. Z-scan measurements at 632.8 nm yielded ${n}_{2}$ $n_{2}$ = 7.583 × 10⁻⁸ m²/W, $\beta$ $β$ = 0.845 × 10⁻⁴ m/W, ${\chi }^{3}$ $χ^{3}$ = 4.172 × 10⁻⁶ esu, and $\gamma$ $γ$ = 2.336 × 10⁻²⁷ esu, with an optical limiting threshold of 15 mW at 532 nm.