Journal of Chemical Crystallography

, Volume 44, Issue 11–12, pp 586–596 | Cite as

Experimental Electron Density of Ammonium Dihydrogen Phosphate in the Paraelectric as well as Antiferroelectric Phases by the Maximum Entropy Method

  • Rajul Ranjan ChoudhuryEmail author
  • R. Chitra
  • Frédéric Capet
  • Pascal Roussel
Original Paper


The experimental electron density of ammonium dihydrogen phosphate (ADP) crystal in the paraelectric phase (155 K) as well as antiferroelectric phase (100 K) is obtained from its high resolution X-ray diffraction data using the maximum entropy method. Marked redistribution of electron density has been observed in ADP crystals as the crystal temperature is lowered below the phase transition temperature Tc = 148 K. The nature of very strong O–H–O hydrogen bonds between phosphate anions changes from an ideal covalent interaction to a polar covalent interaction as the temperature is altered from 155 to 100 K. The influence of intermolecular interaction like the dipolar interaction on the electron density particularly in the intermolecular region is clearly visible in the electron density maps. One of the most striking features of the electron density of ADP is the presence of non nuclear maxima (NNM) within the “ab” planes. It is argued that the appearance of these NNMs is a normal consequence of the chemical bonding between homonuclear groups in ADP.

Graphical Abstract

The manuscript describes the experimental electron density of ammonium dihydrogen phosphate (ADP) obtained from its high resolution X-ray diffraction data recorded at two crystal temperatures namely 100 and 155 K.


Molecular electron density Maximum entropy method Hydrogen bonds 


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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Rajul Ranjan Choudhury
    • 1
    Email author
  • R. Chitra
    • 1
  • Frédéric Capet
    • 2
  • Pascal Roussel
    • 2
  1. 1.Solid State Physics DivisionBhabha Atomic Research CenterMumbaiIndia
  2. 2.CNRS, UMR8181, UCCS, Unité de catalyse et de chimie du solide, ENSCL-USTLUniversité Lille Nord de FranceVilleneuve d’AscqFrance

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