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In this article the authors present an improved form of the force …


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Biology Articles » Biophysics » Water properties from first principles: Simulations by a general-purpose quantum mechanical polarizable force field » Tables

Tables
- Water properties from first principles: Simulations by a general-purpose quantum mechanical polarizable force field

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Table 1. Absolute value of dipole moment (D), eigenvalues of quadrupole (Q1, Q2, Q3), and polarizability (P1, P2, P3) tensors for water molecule

Approach D, Debye Q1 Q2 Q3 P1, Å3 P2, Å3 P3, Å3
(Buckingham)
QMPFF2 1.87 −5.22 0.16 5.04 1.42 1.42 1.42
QM 1.87 −5.02 −0.12 5.14 1.37 1.41 1.48

 

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Table 2. Water multimer energies (kcal/mol) in different optimized conformations

Approach Dimer
Trimer cyclic Tetramer cyclic Pentamer cyclic Hexamer
Linear Cyclic Bifurcate Prism Book Ring
QMPFF2 −5.08 −3.39 −2.56 −15.2 −25.9 −32.9 −43.2 −42.2 −39.9
QM −4.68 −3.68 −2.92 −14.6 −25.4 −33.4 −42.7 −42.1 −41.4
 

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 Table 3. Liquid water properties obtained from MD simulations with QMPFF2 compared with experimental values

Approach E = Eliq − Egas, kcal·mol−1 Cp, cal·mol−1·K−1 105D, cm2·s−1 ρ, g·cm−3 105 α, K−1 ρmax, g·cm−3 Tmax, °C
QMPFF2 (classical MD) −10.9 19.6 1.2 1.003 26 1.005 8
QMPFF2 (quantum MD) −9.6 18.6 1.9 0.992 30 — —
Experimental −9.9 18.0 2.3 0.998 26 1.000 4

E, liquid binding energy; Cp, specific heat capacity; D, diffusion constant; ρ, density; α, coefficient of thermal expansion, all under ambient conditions; ρmax, maximum density; Tmax, temperature of occurrence of ρmax.

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