NMR Spectroscopy of Intermetallic Compounds: An Experimental and Theoretical Approach to Local Atomic Arrangements in Binary Gallides

Abstract

The results of the investigation of MGa(2) with M = Ca, Sr, Ba and of MGa(4) with M = Na, Ca, Sr, Ba by a combined application of NMR spectroscopy and quantum mechanical calculations are comprehensively evaluated. The electric-field gradient (EFG) was identified as the most reliable measure to study intermetallic compounds, since it is accessible with high precision by quantum mechanical calculations and, for nuclear spin I>1/2, by NMR spectroscopy. The EFG values obtained by NMR spectroscopy and quantum mechanical calculations agree very well for both series of investigated compounds. A deconvolution of the calculated EFGs into their contributions reveals its sensitivity to the local environment of the atoms. The EFGs of the investigated di- and tetragallides are dominated by the population of the p(x)-, p(y)-, and p(z)-like states of the Ga atoms. A general combined approach for the investigation of disordered intermetallic compounds by application of diffraction methods, NMR spectroscopy, and quantum mechanical calculations is suggested. This scheme can also be applied to other classes of crystalline disordered inorganic materials.

The Zintl Phase Cs7NaSi8 – From NMR Signal Line Shape Analysis and Quantum Mechanical Calculations to Chemical Bonding

“…The results from FPLO and Wien2k for the calculated DOS were qualitatively identical showing the same contributions as already reported in Rb 7 NaSi 8 . [21] Comparison of QM calculated with experimentally determined NMR coupling parameters from previous studies on intermetallic phases -MGa 2 (M = Ca, Sr, and Ba) , [13] MGa 4 (M = Na, Ca, Sr, and Ba), [14] M 4 Si 4 (M = Na, Rb, K, and Cs) [20] as well as Ba 2 Si 4 [12] and Rb 7 NaSi 8 [21] and NaRb 7 (Si 4-x Ge x ) 2 [22] -indicates that a good agreement can be achieved within the following ranges: Ϯ 10 ppm for the NMR signal shift and shift anisotropy, Ϯ 0.1 MHz for C Q and Ϯ0.1 ϫ 10 21 V m -2 for V ZZ , respectively. In case of asymmetry parameters η ϶ 0, an error of Ϯ 0.05 can be estimated.…”

Unravelling Local Atomic Order of the Anionic Sublattice in M(Al1−xGax)4 with M=Sr and Ba by Using NMR Spectroscopy and Quantum Mechanical Modelling

“…[56,57] Ap owdered sample (50 mg) was sealed in aN ba mpoule in an Ar atmosphere and measured between ambient temperature and 1200 8Ca th eating/cooling rates of 5Kmin À1 . [17,[30][31][32][33] Therefore, the polycrystalline powder samples were mixed with at wo component glue (UHU endfest 300) and filled into quartz glass tubes (diameter = 5mm). [44,58] Solid state NMR spectroscopy NMR sample preparation and measurement techniques:S tatic 27 Al NMR experiments were performed on both regular and magnetically aligned powder samples.…”

“…As ignificantly different c/a ratio within the BaAl 4 type unit cell results. [18,30] The XRD-NMR-QMa pproachw as thereby appliedt ot he binaryI Ps MGa 2 with M = Ca,S r, and Ba [31] and MGa 4 with M = Na, Ca, Sr,a nd Ba [32] to gain insight into the chemical bonding of the Ga atoms. [28,29] The combined application of X-ray diffraction (XRD), solid state nuclearm agnetic resonance (NMR) spectroscopy,a nd quantum mechanical (QM) calculations was recently shown to be wells uited to study the chemical bonding and local atomic environments in ordereda nd disordered IPs.…”

“…Furthermore, we recently showed that this approach is suited tos tudy varying Ga bonding situations due to cation substitution in the solid solution Sr 1Àx Ba x Ga 2 . [17,32] Four-and five-bonded Al(4b)/Ga(4b) and Al(5b)/Ga(5b) atoms, respectively,b uild a3 Dp olyanionic sublattice. [17,[34][35][36][37][38] Herein, we report on the next step by focussing on the differenceo fAl representing at ypical main-group metal versus Ga as an ontypical main-group metal.…”

“…[17,[34][35][36][37][38] Herein, we report on the next step by focussing on the differenceo fAl representing at ypical main-group metal versus Ga as an ontypical main-group metal. [15,17,31,32] As forc ationic disorder in Sr 1Àx Ba x Ga 2 ,amodel of isolated substitution centres (ISC) [33] in the vicinity of low degrees of substitution was carved out. The binaries crystallise in the BaAl 4 type structure in space group I4/mmm ( Figure 1).…”