Thermomechanical, electronic and thermodynamic properties of ZnS cubic polymorphs: anab initioinvestigation on the zinc-blende–rock-salt phase transition

Abstract

In the present work, an extensive and detailed theoretical investigation is reported on the thermomechanical, electronic and thermodynamic properties of zinc‐blende (sphalerite, zb‐ZnS) and rock‐salt zinc sulfide (rs‐ZnS) over a wide range of pressure, by means of ab initio Density Functional Theory, Gaussian type orbitals and the well known B3LYP functional. For the first time, vibrational frequencies, phonon dispersion relations, elasto‐piezo‐dielectric tensor, thermodynamic and thermomechanical properties of rs‐ZnS were calculated with a consistent approach that allows a direct comparison with the low‐pressure polymorph. Special attention was paid to the evaluation of the thermodynamic pressure–temperature stability of the mineral phases between 0–25 GPa and 0–800 K. The static (T = 0 K) bulk moduli of sphalerite and rock‐salt ZnS were 72.63 (3) GPa and 84.39 (5) GPa, respectively. The phase transition in static conditions calculated from the equation of state was about 15.5 GPa, whereas the elastic constants data resulted in Ptrans = 14.6 GPa. At room temperature (300 K), the zb‐rs transition occurs at 14.70 GPa and a negative Clapeyron slope (dP)/(dT) = 0.0023 was observed up to 800 K. The electronic band structure showed a direct band gap for zb‐ZnS (Eg = 4.830 eV at equilibrium geometry), which became an indirect one by increasing pressure above 11 GPa. The results were found to be in good agreement with the available experimental and theoretical data, further extending the knowledge of important properties of zinc sulfide, in particular the thermomechanical ones of the rock‐salt polymorph here extensively explored for the first time.

Study of the variation of the optical properties of calcite with applied stress, useful for specific rock and material mechanics

“…The calculation of the structural, dielectric and (photo)elastic properties were conducted both in static conditions, i.e., at 0 K without any thermal contribution, and at room temperature (298 K) at a pressure of 1 atm (= 0.0001 GPa). For the latter, we employed the quasi-harmonic approximation to introduce the temperature effect on the cited properties, as described in previous literature 48 – 50 . Five unit cell volumes, the equilibrium one, two compressed and two expanded, were used for the quasi-harmonic approximation.…”

Hydroxylapatite and Related Minerals in Bone and Dental Tissues: Structural, Spectroscopic and Mechanical Properties from a Computational Perspective

“…The quasi-harmonic approximation solves this issue by including an explicit dependency of the phonon (vibrational) modes on the unit cell volume of a solid phase. Full details of this approach are beyond the scope of the present review, but the interested reader could find the basic theory, formulations and different kind of implementations in dedicated works [ 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 ]. When applied to hydroxylapatite and carbonated apatite models [ 71 , 72 , 121 ], the quasi-harmonic approximation provided results in even better agreement with the experimental data than the data calculated at 0 K [ 123 ].…”

Упругие свойства нанокристаллических кубических сульфидов Ag-=SUB=-2-=/SUB=-S и ZnS

“…гр. F43m) структурой сфалерита при температуре 300 K можно оценить, используя температурные зависимости изотермического модуля всестороннего сжатия B, представленные в работе [14]. Согласно [14], наклон dB/dT равен −0.0109 GPa • K −1 .…”

“…F43m) структурой сфалерита при температуре 300 K можно оценить, используя температурные зависимости изотермического модуля всестороннего сжатия B, представленные в работе [14]. Согласно [14], наклон dB/dT равен −0.0109 GPa • K −1 . В первом приближении будем полагать, что относительное уменьшение постоянной c 11 с ростом температуры от 0 до 300 K такое же, как уменьшение модуля всестороннего сжатия B. Константы c i j сульфида ZnS при 300 K можно представить как c i j (T ) = c i j (0) + T dc i j /dT .…”

“…Для оценки деформационных искажений на границе раздела между сульфидами серебра и цинка нужны сведения об упругих характеристиках ZnS и Ag 2 S. Упругие свойства кубического ZnS достаточно хорошо известны [10][11][12][13][14]. Низкотемпературная кубическая (пр.…”