Sandia National Laboratories Tramonto

Functional Control Parameters

These are switches that control the density functional equations being studied for a given case. The functional switches are separated into hard sphere, attractive, Coulombic, and polymer functionals.

  • Type_func(int): Hard sphere functional type (for HS perturbation calculations). Options are:
    • -1: NONE: no hard sphere functionals. Set this for ideal gases, Poisson-Boltzman electrolytes, or CMS polymers.
    • 0: FMT1: original FMT functional developed by Rosenfeld (Phys Rev Lett, v.63, p.980, 1989).
    • 1: FMT2: FMT with corrected zero dimensional crossover behavior (Rosenfeld et.al., Phys. Rev. E., v.55, p.4245, 1997 and Rosenfeld et.al., J. Phys. Cond. Matt., v.8, p.L577, 1996).
    • 2: FMT3: White Bear Functional (Roth et.al., J. Phys. Cond. Matt., v.14, p.12063, 2002)
  • Type_attr(int): Define longer range (often but not always attractive) interactions. if Type_attr> -1, then Type_pairPot must be defined. Options are:
    • -1: NONE: no longer range interactions.
    • 0: MFPAIR1: Strict mean field interactions (see Egorov, Phys.Rev.E., v.70, p.031402, 2004 for an example based on an extended Yukawa potential). Note that this option can also be used to add attractions to CMS polymer calculations (see Frink and Frischknecht, Phys.Rev.E, v.72, p.041923, 2005 for an example of how this has been implemented.)
    • 1: MFPAIR2: Strict mean field interactions with a Barker-Henderson modification to the hard-core diameter.
  • Type_pairPot(int): Type of potential to be used for calculation with a strict mean field extended interactions.
    • 0: PAIR_LJ12_6_CS: Cut and shifted 12-6 Lennard-Jones potential.
    • 1: PAIR_COULOMB_CS: Cut and shifted Coulomb potential (note ... this is generally a bad idea - turn on Type_coul instead to preserve charge neutrality.
    • 2: PAIR_COULOMB: Full Coulomb potential used in forming integration stencils. (note ... this is still approximate and a bad idea - again turn on Type_coul instead to preserve charge neutrality.
    • 3: PAIR_YUKAWA_CS: Cut and shifted Yukawa potential (defined as in Egorov, Phys.Rev.E., v.70, p.031402, 2004).
  • Type_coul(int): Type of potential to be used to treat electrostatics for cases where the electrostatic potential is introduced into the system of equations, and Poisson's equation is solved simultaneously with the DFT Euler-Lagrange equations. Options are:
    • -1: NONE: turn off Poisson Terms. Do this for neutral systems or for Type_pairPot=1 or 2.
    • 0: BARE: Mean field electrostatics based on point charges only (no other correlations included).
    • 1: DELTAC: Mean field electrostatics for point charges plus a 2nd order correction based on an analytical solution for the RPM using the mean spherical approximation (MSA) for the special case of a restricted primitive model (RPM) where all charged species have identical size. (see Tang and Davis, J.Chem. Phys. 1989).
    • 2: POLARIZE: Electrostatics for a polarizeable fluid. Implemented only in 1D as of the 2007 release of Tramonto v2.1.
  • Type_poly(int): The type of functional to be used to describe bonded systems. Note that long range interactions and electrostatics can be turned on in conjunction with bonded systems by turning on Type_attr and/or Type_coul as described above. Furthermore note that the WTC polymers also requires a selection of the reference hard sphere fluid type using Type_func above. Options for Type_poly are:
    • -1: NONE: No polymer functionals. No bonds.
    • 0: CMS: Chandler-McCoy-Singer DFT (J.Chem.Phys., v.85, p. 5971, 1986; v.85, p.5977, 1986; v. 87, p.4853, 1987) based on freely-jointed chains where the single chain part of the functional is evaluated numerically as described by Doneley et.al. (see Doneley et.al. J. Chem. Phys., v.103, p.5061, 1995; and Frischknecht et.al., J. Chem. Phys., v. 117, 10385, 2002).
    • 1: CMS_SCFT: This option simplifies the CMS theory to reproduce polymer Self-Consistent Field Theory. Note that the algorithms in Tramonto are not optimal for SCFT. Rather this approach serves as a test and a point of comparison with work in the SCFT community. This option is not fully implemented as of the 2007 release of Tramonto v2.1.
    • 2: WTC: Tripathi-Chapman functionals based on a Wertheim's theory approach in the limit of infinitely strong associations (see Tripathi and Chapman, Phys. Rev. Lett., v.94, p. 087801, 2005 and J. Chem. Phys., v.122, p.094506, 2005).