MCCCS Towhee (example manual)

 

 

Overview
    This section describes the examples included with the current download version of Towhee and gives some tips for getting started with these examples.
General Tips
    All of the example files are found in the Examples directory that comes with the default download package. You will find a file named answer_current in each directory and that contains the testing output for each example. Tests for version 3.14.9 and later were run using gcc version 3.2.2 with the FFLAGS=-fbounds-check option in the configure script. While this is a great option for debugging we suggest letting the configure option determine the optimization level automatically when compiling the code for production runs. The -O2 level of optimization results in noticable improvements in the code speed. Starting with version 4.13.1, the compile-time flag --enable-safe-compare attempts to minimize differences in the output between platforms, but should not be used for production runs.

    Each of the towhee_input files has to specify the complete path of the force field files it wishes to utilize. The default setting is something like /towheebase/ForceFields/towhee_ff_Charmm22 where Charmm22 would be the force field you are using. You can either change the /towheebase section to be the directory path for the ForceFields file, or you can set a symbolic link for /towheebase using the standard unix command
      ln -s /Your/Actual/Directory /towheebase

    As an alternative to either manually modifying the ForceFields files or creating symbolic links, execute the relocate_examples.pl script in the Examples directory. This script copies all the examples to a directory named test in the towhee root directory, and will simultaneously rewrite all references to /towheebase appropriately. You can then execute examples in the normal fashion from the test directory.

    To run the code you need to be in one of the example directories and then execute a command similar to /towheebase/Source/towhee where again /towheebase is replaced by your actual directory structure.
Descriptive List of Examples
  • Amber_IsoPropanol
      A two box NVT Gibbs ensemble that demonstrates the setup for determining single-component vapor-liquid coexistence. Uses the Lennard-Jones potential and the Amber96 force field.
  • Amber_Villin
      A single box simulation of a short peptide chain in vacuum to demonstrate the use of the protien builder functionality. Uses the Lennard-Jones potential and the Amber96 force field.
  • Au_Cu_Switch
      A single box simulation demonstrating the use of the center-of-mass switch move for a mixture of monatomic metal molecules with an EAM potential.
  • AVB1_Methane
      A single box simulation that demonstrates the use of the agregation-volume-bias move type 1. Uses the Lennard-Jones potential and the TraPPE-UA force field.
  • Catlow_Zeolite_4a
      A two box, multi-component simulation demonstrating the setup for computing adsorption isotherms in porous materials. Uses the combined exponential-6 and Lennard-Jones potential and the Catlow force field.
  • Charmm19_ubiquitin
      A single box simulation that demonstrates the use of the Charmm19-EEF1 potential with implicit water solvation for a protein.
  • Charmm22_Ethanethiol
      A single box simulation that demonstrates how to compute a liquid density using the isobaric-isothermal ensemble. Uses the Lennard-Jones potential and the Charmm22 force field.
  • Charmm27_Heme
      A single box simulation that shows how to set up a Heme group in Charmm27 using the atom builder.
  • Charmm27_NA
      A single box simulation that shows how to set up a nucleic acid in Charmm27 using the nucleic acid builder.
  • Charmm27_Polyalanine
      A single box single molecule simulation that demonstrates the use of the 'helix cbmc' initialization option. This builds a polypeptide with the C&alpha atoms in a helix of specified radius and angle and then grows the rest of the atom using configurational-bias.
  • Compass_Methanol
      A single box, single molecule simulation that demonstrates how to compute the energy for a single molecule in vacuum by disabling the Ewald sum. Uses the 9-6 potentials and the Compass force field.
  • Convert/LAMMPS_class2
      Demonstrates the conversion of LAMMPS files into Towhee input files. To perform this conversion change the first line of the towhee_input file to the 'LAMMPS' inputformat instead of the 'Towhee' inputformat. Running Towhee will create files suitable for a real Towhee run. Copy these as instructed by the code and then run again to perform a Towhee simulation with the new files. Uses the 9-6 force field.
  • Convert/LAMMPS_decane
      Demonstrates the conversion of LAMMPS files into Towhee input files. To perform this conversion change the first line of the towhee_input file to the 'LAMMPS' inputformat instead of the 'Towhee' inputformat. Running Towhee will create files suitable for a real Towhee run. Copy these as instructed by the code and then run again to perform a Towhee simulation with the new files. Uses the Lennard-Jones force field.
  • Convert/LAMMPS_lc
      Demonstrates the conversion of LAMMPS files into Towhee input files. To perform this conversion change the first line of the towhee_input file to the 'LAMMPS' inputformat instead of the 'Towhee' inputformat. Running Towhee will create files suitable for a real Towhee run. Copy these as instructed by the code and then run again to perform a Towhee simulation with the new files. Uses the Lennard-Jones force field.
  • Cu_Pb_EAM
      A single box simulation using the embedded atom potential for a mixture of copper and lead.
  • Cu_VLE
      A two box simulation using the embedded atom potential to compute vapor-liquid coexistence for copper.
  • DFT_Field
      Test case that combines Towhee with the Tramonto package as an implicit solvent. The Tramonto package is not yet publicly available.
  • Dick1994_PETN
      An example that shows how to construct an initial system by replicating a unit cell. Creates a PETN solid using the Dick and Ritchie 1994 force field.
  • DREIDING
      An example that shows how to minimize an initial structure by using single atom translations and a low temperature. Uses the DREIDING force field.
  • Energy_Biasing
      An example that shows how to set up the input files to create a towhee_map file to utilize energy biasing for adsorption of molecules in porous materials. Uses the Dubb2004 force field.
  • EPM_VLCC
      An example of a single-component vapor-liquid coexistence simulation taken from Table 4 of Harris and Yung 1995. Uses the Lennard-Jones potential and the EPM2 force field.
  • FENE_Hexamer
      An example using the FENE bond potential for a simple Lennard-Jones hexamer.
  • Formamide_Scaled
      A one box, two component simulation that demonstrates how to perform a simulation with a 'Scaled Lennard-Jones' classical potential.
  • Fris_Walls
      A one box, single component simulation that demonstrates how to perform a simulation between Lennard-Jones walls with additional hard walls and an "umbrella" potential.
  • Gordon
      A single box, single component simulation just to check that the Gordon n-6 potential gives the same energies and pressures as the Lennard-Jones potential when n is set to 12.
  • Gromos_Isobutane
      A two box, single component simulation that demonstrates how to perform a single-component vapor-liquid coexistence curve. Uses the Lennard-Jones potential and the Gromos43A1 force field.
  • Gromos_Methylpropylsulfide
      A single box, single component simulation that demonstrates how to determine liquid densities. Uses the Lennard-Jones potential and the Gromos43A1 force field.
  • Hard_Sphere
      A single box, multicomponent simulation of hard spheres. Uses the Hard Sphere potential and force field.
  • Henry Law
      A single box, multicomponent simulation designed to measure the Henry's Law coefficient of four small gases in a liquid ethanol solvent. This example reproduces the results from the winner of the Second Industrial Fluids Simulation Challenge Problem 2 involving the Henry's law coefficient for methane, O2, N2 and CO2 in ethanol using a combination of the TraPPE-UA, TraPPE-EH, and Coon1987 force fields. I suggest using an nstep value of 50000 and a blocksize of 10000 for production runs of this system as the chemical potential is challenging to compute precisely with Widom insertion.
  • Histogram
      This directory contains three subdirectories (Phase, PVT, Weights) that each illustrate one aspect of the analyse_histogram routine. This routine is used to process the output from grand canonical simulations using the Histogram Reweighting method. Please see the README.histogram file in the Examples/Histogram directory for more information.
  • Ideal_Chain
      A single box, single component demonstration of the configurational-bias algorithm for a flexible ideal chain in the isothermal-isobaric ensemble. Uses the Hard Sphere potential with the zero diameter hard sphere force field.
  • MM2_Ethane
      A two box simulation of ethane using the MM2 force field.
  • NaCl_1x1x1
      A single box computation of the Madelung constant to verify the accuracy of the Ewald summation. The correct answer is 1.747558 (dimensionless) and this example allows the user to modify the parameters of the Ewald sum and see how this affects the accuracy of the total coulombic energy.
  • OPLS_Propanamide
      A single box single component liquid density determination. Uses the Lennard-Jones potential and the OPLS-aa force field.
  • Parallel_Test
      An example of how to use the towhee_parallel file with the mpitowhee version of the code to run multiple simulations on one or more processors.
  • Potter_CF2H2
      An example of the 'LB plus manual' classical mixing rule applied to reproduce a two box vapor-liquid coexistence point using the Potter et al. 1997 force field.
  • Shukla_Gasses
      An example of the 'Skukla' classical mixing rule for a trivial simulation containing four different small molecules in the gas phase using the Shukla 1987 force field.
  • SKS_Pentane
      An example from the literature to illustrate the calculation of vapor-liquid coexistence using the SKS potential for n-alkanes. Also serves as a test case for rotational-bias and configurational-bias 2 box swap moves.
  • Small_Peptide
      An example of how to create a small peptide with the initial structure generated via CBMC.
  • SMMKmain_2244688nonane
      An example of how to create an initial structure of 2,2,4,4,6,8,8-heptamethyl nonane using the SMMKmain forcefield. Also serves as a test of the special one-five interactions.
  • SMMKnaip_Ethylpentane
      An example of how to create an initial system suitable for 2-box Gibbs ensemble determination of vapor-liquid coexistence of 3-ethylpentane using the SMMKnaip forcefield. Equilibrating this starting structure (likely several runs of 10,000 cycles) should result in agreement with the densities reported in Table 3 of Siepmann et al. 1997.
  • Solid_LJium
      A simulation of solid Lennard-Jonesium to demonstrate the use of the plane shift and row shift moves.
  • Square_Well_Chain
      A single box, single component demonstration of the configurational-bias algorithm for a tangent sphere square well chain in the canonical ensemble. Uses the Square Well potential with the generic SquareWell force field.
  • Steele_Wall
      A single box, single component demonstration of the Steele surface potential with the Last1993 Lennard-Jones potential in the grand canonical ensemble.
  • SW_Silicon
      An example of how to scan a database of solid structures and compute the energies. This example can also be modified to scan multiple parameters of a force field and compute the RMS differences from the database entries. Uses the Stillinger-Weber potential and the Stillinger-Weber Silicon force field.
  • TMMC
      Examples (Lennard-Jones and SPC/E Water) for performing grand-canonical transition-matrix Monte Carlo (TMMC).
  • TraPPE_Isomers
      Two butene isomers that demonstrate the builder features that allow the user to specify the difference between cis and trans dihedrals using the TraPPE-UA forcefield.
  • TraPPE_Molecules
      A batch of single molecule structures to test the assembler and bond increment method for the TraPPE-UA force field and to test the center-of-mass switch move for polyatomic molecules.
  • TraPPE_Pentane
      An example of a single-component vapor-liquid coexistence simulation. Uses the Lennard-Jones potential and the TraPPE-UA force field.
  • Triglycerid
      A setup example showing how to build the simple triglyceride model from the Sum et al. paper using the Sum2003 forcefield.
  • UFF
      An example that shows how to minimize an initial structure by using single atom translations and a low temperature. Uses the UFF force field.
  • uVT_Ethane
      An example of a grand canonical ensemble simulation with the output flags set to generate towhee_histogram files.
  • VLCC_Fit
      A set of README documents and data files that provides an example of how to use the fitcoex utility program to analyse a set of towhee_vlcc output files to extrapolate a critical temperature and critical density for a single component system and compare that graphically to experimental data. This requires the fitcoex utility program to process the files and the plot script uses the freely available xmgrace program to graph the results.
  • Wall_Water
      An example of use of fields in Towhee. Demonstrates water between two hard walls.
  • Walt2001_Nanotube
      An example showcasing the nanotube builder functionallity. Grand canonical ensemble simulation with a single nanotube and the chemical potential set to fill the simulation box with water.
  • Weiner1984
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Send comments to: Marcus G. Martin

Last updated: June 17, 2009