The nuclear quadrupole moments of 191,193,195,197Pb and 139La

Local Structure in Disordered Melilite Revealed by Ultrahigh Field 71Ga and 139La Solid‐State Nuclear Magnetic Resonance Spectroscopy

“…To investigate configurational disorder, static 139 La QCPMG spectra were also recorded at 35.2 T (Figure 4a–b). Relatively broad signals with breadths of approximately 700 kHz are observed for both LaSrGa 3 O 7 and La 1.54 Sr 0.46 Ga 3 O 7.27 owing to the large nuclear electric quadrupole moment of 139 La ( Q ( 139 La)=0.206(4)×10 28 m 2 as opposed to Q ( 71 Ga)=0.107(1)×10 28 m 2 ) [26–29] . Comparison between the spectral lineshapes captured for LaSrGa 3 O 7 and La 1.54 Sr 0.46 Ga 3 O 7.27 is compelling evidence for enhanced disorder in the La 3+ ‐doped phase.…”

“…Relatively broad signals with breadths of approximately 700 kHz are observed for both LaSrGa 3 O 7 and La 1.54 Sr 0.46 Ga 3 O 7.27 owing to the large nuclear electric quadrupole moment of 139 La (Q ( 139 La) = 0.206(4)×10 28 m 2 as opposed to Q ( 71 Ga) = 0.107(1)×10 28 m 2 ). [26][27][28][29] Comparison between the spectral lineshapes captured for LaSrGa 3 O 7 and La 1.54 Sr 0.46 Ga 3 O 7.27 is compelling evidence for enhanced disorder in the La 3 + -doped phase. Despite the challenges associated with the computational treatment of heavy elements such as 139 La, the experimental data are importantly in close agreement with the 139 La spectra predicted from the NMR parameters computed using the ensemble-based approach presented above and the Zeroth-Order Regular Approximation (ZORA) [30] to treat scalar relativistic effects (Figure 4c-d).…”

“…The C Q parameters for 139 La were calculated using the revised nuclear electric quadrupole moment Q ( 139 La) = 0.206(4)×10 28 m 2 . [27][28][29] To facilitate comparison between computed and experimental results, the isotropic and anisotropic chemical shifts (δ iso,cs and δ aniso,cs , respectively) were determined from the computed isotropic chemical shielding σ iso,cs and anisotropic chemical shielding σ aniso,cs using δ iso,cs = σ ref + m σ iso,cs and δ aniso,cs = m σ aniso,cs , with σ ref ( 71 Ga) = 1442.22 ppm, m ( 71 Ga) = À 0.821, σ ref ( 139 La) = 3460.92 ppm and m ( 139 La) = À 0.681. The σ ref and m values were calculated using a standard procedure which also aims at reducing the systematic errors in the calculations.…”

Cation Distribution and Anion Transport in the La3Ga5–xGe1+xO14+0.5x Langasite Structure

“…Further information on the La 3 Ga 5– x Ge 1+ x O 14+0.5 x local structure can be provided by solid-state 139 La NMR spectroscopy. Owing to its large nuclear electric quadrupole moment of (0.206 ± 0.004) × 10 –28 m 2 , 139 La is usually subject to strong quadrupolar interactions which result in anisotropically broadened NMR resonances, thereby motivating the use of the highest available fields to achieve enhanced resolution. − Static 139 La NMR spectra of La 3 Ga 5 GeO 14 and La 3 Ga 3.5 Ge 2.5 O 14.75 recorded at 35.2 T are shown in Figure . One relatively broad signal in the region of the spectrum between −800 and 1200 ppm is observed for both La 3 Ga 5 GeO 14 and La 3 Ga 3.5 Ge 2.5 O 14.75 , with the signal obtained for La 3 Ga 5 GeO 14 also exhibiting one shoulder at high frequencies.…”

“…The quadrupolar coupling constant C normalQ = eQV zz h and quadrupolar asymmetry parameter η normalQ = V xx − V yy V zz are commonly used to express V , where Q is the nuclear electric quadrupole moment, h is the Planck constant, and e is the electron charge. The C Q values for 139 La were calculated using Q ( 139 La) = (0.206 ± 0.004) × 10 –28 m 2 , − while C Q values for the other spins were calculated using the Q values implemented in CASTEP 20.11 (see Table S1).…”