More Like this

1. Crystal and Electronic Structure and Optical Properties of AE 2 SiP 4 ( AE = Sr, Eu, Ba) and Ba 4 Si 3 P 8

   https://doi.org/10.1002/zaac.201800430  

   Mark, Justin ; Dolyniuk, Juli‐Anna ; Tran, Nhon ; Kovnir, Kirill ( November 2018 , Zeitschrift für anorganische und allgemeine Chemie)

   Three new compounds in theAE‐Si‐P (AE= Sr, Eu, Ba) systems are reported. Sr₂SiP₄and Eu₂SiP₄, the first members of their respective ternary systems, are isostructural to previously reported Ba₂SiP₄and crystallize in the noncentrosymmetricI42d(no. 122) space group. Ba₄Si₃P₈crystallizes in the new structure type, inP2₁/c(no. 14) space group,mP‐120 Pearson symbol, Wyckoff sequencee³⁰. In the crystal structures of Sr₂SiP₄and Eu₂SiP₄all SiP₄tetrahedral building blocks are connected via formation of P–P bonds forming a three‐dimensional framework. In the crystal structure of Ba₄Si₃P₈, Si‐P tetrahedral chains formed by corner‐sharing, edge‐sharing, and P–P bonds are surrounded by Ba cations. This results in a quasi‐one‐dimensional structure. Electronic structure calculations and UV/Vis measurements suggest that theAE₂SiP₄(AE= Sr, Eu, Ba) are direct bandgap semiconductors with bandgaps of ca. 1.4 eV and have potential for thermoelectric applications.

    

   more » « less
2. Upper Crustal Structure and Magmatism in Southwest Washington: V p , V s , and V p / V s Results From the iMUSH Active‐Source Seismic Experiment

   https://doi.org/10.1029/2018JB016203  

   Kiser, E. ; Levander, A. ; Zelt, C. ; Schmandt, B. ; Hansen, S. ( July 2019 , Journal of Geophysical Research: Solid Earth)

   Structural details of the crust play an important role in controlling the distribution of volcanic activity in arc systems. In southwest Washington, several different regional structures associated with accretion and magmatism have been invoked to explain the broad distribution of Cascade volcanism in this region. In order to image these regional structures in the upper crust, Pg and Sg travel times from the imaging Magma Under St. Helens (iMUSH) active‐source seismic experiment are inverted forV_p,V_s, andV_p/V_smodels in the region surrounding Mount St. Helens. Several features of these models provide new insights into the regional structure of the upper crust. A large section of the Southern Washington Cascades Conductor is imaged as a lowV_p/V_sanomaly that is inferred to represent a broad sedimentary/metasedimentary sequence that composes the upper crust in this region. The accreted terrane Siletzia is imaged west of Mount St. Helens as north/south trending highV_pandV_p/V_sbodies. TheV_p/V_smodel shows relatively highV_p/V_sregions near Mount St. Helens and the Indian Heaven Volcanic Field, which could be related to the presence of magmatic fluids. Separating these two volcanic regions below 6‐km depth is a northeast trending series of highV_pandV_sbodies. These bodies have the same orientation as several volcanic/magmatic features at the surface, including Mount St. Helens and Mount Rainier, and it is argued that these high‐velocity features are a regional‐scale group of intrusive bodies associated with a crustal weak zone that focuses magma ascent.

    

   more » « less
3. Sr(Ag 1−x Li x ) 2 Se 2 and [Sr 3 Se 2 ][(Ag 1−x Li x ) 2 Se 2 ] Tunable Direct Band Gap Semiconductors

   https://doi.org/10.1002/ange.202301191  

   Zhou, Xiuquan ; Wilfong, Brandon ; Chen, Xinglong ; Laing, Craig ; Pandey, Indra R. ; Chen, Ying‐Pin ; Chen, Yu‐Sheng ; Chung, Duck‐Young ; Kanatzidis, Mercouri G. ( February 2023 , Angewandte Chemie)

   Synthesizing solids in molten fluxes enables the rapid diffusion of soluble species at temperatures lower than in solid‐state reactions, leading to crystal formation of kinetically stable compounds. In this study, we demonstrate the effectiveness of mixed hydroxide and halide fluxes in synthesizing complex Sr/Ag/Se in mixed LiOH/LiCl. We have accessed a series of two‐dimensional Sr(Ag_1−xLi_x)₂Se₂layered phases. With increased LiOH/LiCl ratio or reaction temperature, Li partially substituted Ag to form solid solutions of Sr(Ag_1−xLi_x)₂Se₂withxup to 0.45. In addition, a new type of intergrowth compound [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] was synthesized upon further reaction of Sr(Ag_1−xLi_x)₂Se₂with SrSe. Both Sr(Ag_1−xLi_x)₂Se₂and [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] exhibit a direct band gap, which increases with increasing Li substitution (x). Therefore, the band gap of Sr(Ag_1−xLi_x)₂Se₂can be precisely tuned via fine‐tuningxthat is controlled by only the flux ratio and temperature.

    

   more » « less
4. Sr(Ag 1−x Li x ) 2 Se 2 and [Sr 3 Se 2 ][(Ag 1−x Li x ) 2 Se 2 ] Tunable Direct Band Gap Semiconductors

   https://doi.org/10.1002/anie.202301191  

   Zhou, Xiuquan ; Wilfong, Brandon ; Chen, Xinglong ; Laing, Craig ; Pandey, Indra R. ; Chen, Ying‐Pin ; Chen, Yu‐Sheng ; Chung, Duck‐Young ; Kanatzidis, Mercouri G. ( February 2023 , Angewandte Chemie International Edition)

   Synthesizing solids in molten fluxes enables the rapid diffusion of soluble species at temperatures lower than in solid‐state reactions, leading to crystal formation of kinetically stable compounds. In this study, we demonstrate the effectiveness of mixed hydroxide and halide fluxes in synthesizing complex Sr/Ag/Se in mixed LiOH/LiCl. We have accessed a series of two‐dimensional Sr(Ag_1−xLi_x)₂Se₂layered phases. With increased LiOH/LiCl ratio or reaction temperature, Li partially substituted Ag to form solid solutions of Sr(Ag_1−xLi_x)₂Se₂withxup to 0.45. In addition, a new type of intergrowth compound [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] was synthesized upon further reaction of Sr(Ag_1−xLi_x)₂Se₂with SrSe. Both Sr(Ag_1−xLi_x)₂Se₂and [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] exhibit a direct band gap, which increases with increasing Li substitution (x). Therefore, the band gap of Sr(Ag_1−xLi_x)₂Se₂can be precisely tuned via fine‐tuningxthat is controlled by only the flux ratio and temperature.

    

   more » « less
5. Raman spectral behavior of N 2 , CO 2 , and CH 4 in N 2 –CO 2 –CH 4 gas mixtures from 22°C to 200°C and 10 to 500 bars, with application to other gas mixtures

   https://doi.org/10.1002/jrs.6033  

   Sublett, Jr, D. Matthew ; Sendula, Eszter ; Lamadrid, Hector M. ; Steele‐MacInnis, Matthew ; Spiekermann, Georg ; Bodnar, Robert J. ( November 2020 , Journal of Raman Spectroscopy)

   The Raman spectral behavior of N₂, CO₂, and CH₄in ternary N₂–CO₂–CH₄mixtures was studied from 22°C to 200°C and 10 to 500 bars. The peak position of N₂in all mixtures is located at lower wavenumbers compared with pure N₂at the same pressure (P)–temperature (T) (PT) conditions. The Fermi diad splitting in CO₂is greater in the pure system than in the mixtures, and the Fermi diad splitting increases in the mixtures as CO₂concentration increases at constantPandT. The peak position of CH₄in the mixtures is shifted to higher wavenumbers compared with pure CH₄at the samePTconditions. However, the relationship between peak position and CH₄mole fraction is more complicated compared with the trends observed with N₂and CO₂. The relative order of the peak position isotherms of CH₄and N₂in the mixtures in pressure–peak position space mimics trends in the molar volume of the mixtures in pressure–molar volume space. Relationships between the direction of peak shift of individual components in the mixtures, the relative molar volumes of the mixtures, and the attraction and repulsion forces between molecules are developed. Additionally, the relationship between the peak position of N₂in ternary N₂–CO₂–CH₄mixtures with pressure is extended to other N₂‐bearing systems to assess similarities in the Raman spectral behavior of N₂in various systems.

    

   more » « less