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Complex interplay of interatomic bonding in a multi-component pyrophosphate crystal: K2Mg (H2P2O7)2·2H2O

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      The electronic structure and interatomic bonding of pyrophosphate crystal K 2Mg (H 2P 2O 7) 2·2H 2O are investigated for the first time showing complex interplay of different types of bindings. The existing structure from single-crystal X-ray diffraction is not sufficiently refined, resulting in unrealistic short O─H bonds which is rectified by high-precision density functional theory (DFT) calculation. K 2Mg (H 2P 2O 7) 2·2H 2O has a direct gap of 5.22 eV and a small electron effective mass of 0.14 m e. Detailed bond analysis between every pair of atoms reveals the complexity of various covalent, ionic, hydrogen bonding and bridging bonding and their sensitive dependence on structural differences. The K--O bonds are much weaker than Mg--O bonds and contributions from the hydrogen bonds are non-negligible. Quantitative analysis of internal cohesion in terms of total bond order density and partial bond order density divulges the relative importance of different types of bonding. The calculated optical absorptions show multiple peaks and a sharp Plasmon peak at 23 eV and a refractive index of 1.44. The elastic and mechanical properties show features unique to this low-symmetry crystal. Phonon calculation gives vibrational frequencies in agreement with reported Raman spectrum. These results provide new insights indicating that acidic pyrophosphates could have a variety of unrealized applications in advanced technology.

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          The Elastic Behaviour of a Crystalline Aggregate

           R. Hill (1952)

            Author and article information

            [1 ]Department of Physics and Astronomy, University of Missouri Kansas City , Kansas City, MO 64110, USA
            [2 ]Department of Physics, Laboratory of Optoelectronics and Physical Chemistry of Materials, Faculty of Sciences, University lbn Tofail , Kenitra, Morocco
            [3 ]Laboratory of Condensed Matter and Interdisciplinary Sciences (LAMCSCI), Faculty of Sciences, University Mohammed V , Rabat, Morocco
            Author notes
            Author for correspondence: Wai-Yim Ching e-mail: chingw@

            This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance.

            Electronic supplementary material is available online at

            R Soc Open Sci
            R Soc Open Sci
            Royal Society Open Science
            The Royal Society Publishing
            December 2017
            6 December 2017
            6 December 2017
            : 4
            : 12
            5750006 10.1098/rsos.170982 rsos170982
            © 2017 The Authors.

            Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.

            Funded by: School of Graduate Studies at UMKC;
            Funded by: DOE;
            Award ID: DE-AC03-76SF00098
            Research Article
            Custom metadata
            December, 2017


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