Stable and metastable crystal structures and ammonia dynamics in strontium chloride ammines

Samet Demir, Gözde İniş Demir, Mehmet Çankaya, Adem Tekin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Metal halide ammines are promising ammonia storage materials due to their high ammonia densities and suitable decomposition properties. Here, we studied the polymorphism of ammines with a general formula of Sr(NH3)nCl2 (n = 1, 2, 4, 6, and 8) by combining the Fast and Flexible CrystAl Structure Predictor (FFCASP) with density functional theory (DFT) calculations. Furthermore, the lattice stability and the minimum energy paths for bulk and surface diffusion of NH3 were investigated by performing phonon and nudged elastic band (NEB) calculations. In addition to the successful reproduction of the reported experimental crystal structures of octammine (Pnma (IT number 62)), diammine (Aem2 (IT number 39)) and monoammine (Cmcm (IT number 63)), several isoenergetic polymorphs for each phase were also found. Not only the experimentally determined octammine and monoammine structures, but also the proposed structures for the hexammine and tetrammine phases were found to be metastable. While phonon calculations show instability for the experimental diammine structure, some of the proposed structures for the diammine phase showed thermodynamical stability. Moreover, NEB paths examining the bulk and surface diffusion of NH3 are in accordance with the experimental desorption enthalpies.

Original languageEnglish
Pages (from-to)28282-28295
Number of pages14
JournalPhysical Chemistry Chemical Physics
Volume25
Issue number41
DOIs
Publication statusPublished - 18 Sept 2023

Bibliographical note

Publisher Copyright:
© 2023 The Royal Society of Chemistry.

Funding

Computing resources are provided by the National Center for High Performance Computing of Turkey (UHeM), under Grant Number 1002132012, TÜBİTAK ULAKBİM, High Performance and Grid Computing Center (TRUBA resources) and Informatics Institute of İstanbul Technical University. This work is also funded by the Scientific Research Fund of İstanbul Technical University (Project Number: 38312).

FundersFunder number
National Center for High Performance Computing of Turkey
Ulusal Yüksek Başarımlı Hesaplama Merkezi, Istanbul Teknik Üniversitesi1002132012
Istanbul Teknik Üniversitesi38312

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