Open AccessStructural, Vibrational and Thermodynamic Characteristics of Nacl Single-Molecule Dissolution in Water: A DFT Study
Author(s) -
Mudar Ahmed Abdulsattar,
Abeer H. Khalid,
Yahya M. Abdul-Hussein
Publication year - 2021
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1818/1/012045
Subject(s) - molecule , enthalpy , ion , chemistry , solvation , natural bond orbital , gibbs free energy , density functional theory , solvation shell , analytical chemistry (journal) , crystallography , computational chemistry , thermodynamics , physics , organic chemistry , chromatography
The solvation of a single NaCl molecule in water molecules is discussed using density functional theory. As we add H 2 O molecules, the distance between Na and Cl ions increases. Six H 2 O molecules are enough to make both the distances between Na and Cl ions with nearest O atoms (in H 2 O molecule) less than Na-Cl distance. Natural bond analysis (NBO) shows that absolute charges on Na and Cl ions decrease as we add H 2 O molecules with the absolute charge on Na ion slightly less than Cl ion. The energy gap increases and approaches the experimental energy gap of liquid water at 6.9 eV. Both Gibbs free energy and enthalpy are negative indicating that the reaction is spontaneous and exothermic. The enthalpy converges to the value of the solvation of both Na and Cl ions in water. The negative sign of the entropy indicates order reaction. The Raman vibrational spectra changes from the single vibrational mode at 341.93 cm −1 of NaCl molecule and three H 2 O molecule vibrational modes at 1584, 3863.9, and 3778 cm −1 to three multi bands centred at 500, 1600 and 3400 cm −1 for NaCl with 9 H 2 O molecules with the diminishing of Na-Cl vibration intensity.