Semiconductors

NMR of monoclinic silver sulfide $\alpha$-Ag$_2$S

A. A. Valeeva^a, K. N. Mikhalev^b, E. V. Suvorkova^b, S. I. Sadovnikov^a, A. I. Gusev<sup>a

a</sup> Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Ekaterinburg
^b Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg

Abstract: The structure of monoclinic silver sulfide powder $\alpha$-Ag$_2$S has been studied for the first time by the NMR method on $^{109}$Ag nuclei. It has been established that the NMR spectrum of $^{109}$Ag monoclinic sulfide $\alpha$-Ag$_2$S is a single narrow line, the width of which varies slightly with temperature in the range of 85–295 K. At temperatures below 200 K, a significant increase in the isotropic component of the shear tensor $K_{\text{iso}}$ of $^{109}$Ag nuclei in the Ag$_2$S powder is observed. An anomalously low value of the spin-spin relaxation time $T_2$ on $^{109}$Ag nuclei has been detected. Using modeling, it has been shown that with decreasing temperature in silver sulfide, in addition to the acanthite described in the literature, other phases of silver sulfide Ag$_2$S, derivatives of high-temperature argentite $\beta$-Ag$_2$S and having other structures, can form. It is shown that in the band structure of all model predicted Ag$_2$S phases, a forbidden band with a width of 0.6–1.5 eV is observed, indicating their semiconductor properties.

Keywords: silver sulfide, $^{109}$Ag isotope, isotropic shift, spin-spin relaxation time, predicted low-temperature Ag$_2$S phases.

Received: 30.01.2025
Revised: 31.01.2025
Accepted: 02.02.2025

DOI: 10.61011/FTT.2025.02.59978.21-25

 English version: Physics of the Solid State, 2025, 67:2, 254–258

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