surfe.xm

一个很好的分子动力学程序

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#  Example: Calculate the surface energy of a 100 surface in Ni at 0K #
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#  METHOD                                                             #
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#  Compare the energy of a lattice with no surface (repeating         #
#  boundary conditions in three directions) with the energy of a      #
#  lattice with one surface (repeating boundaries in two              #
#  direction, a free surface in the other).  The difference in        #
#  energy will be due to the surface energy.  Divide the energy       #
#  difference by the surface area to get the surface energy.          #
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#  Read in NiAl potential
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read ../niai.txt
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#  Set the size of the simulation box
#    NX,NY,NZ are the number of unit cells in the X, Y and Z directions
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calc NX=4
calc NY=4
calc NZ=4
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#  Create an FCC lattice with unit cell length of 1 angstrom
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box NX NY NZ
fill particle 4
1  1/4  1/4  1/4
1  1/4  3/4  3/4
1  3/4  1/4  3/4
1  3/4  3/4  1/4
fill go
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#   Scale lattice to unit cell length of Ni, 3.52 angstroms
#   Save scale factor in the variable SCALE for later use.
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calc  SCALE=3.52
scale SCALE
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#  Write lattice energy per atom with repeating boundaries in three directions
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surface off x y z
write energy
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#  Write lattice energy per atom with free surface in x direction
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surface on x
write energy
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#  Calculate area of free surface (in angstroms)
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#     NX and NZ are the number of unit cells in the Y and Z directions
#     2  is the number of surfaces (one each at X=0 and X=NX*SCALE)
#     SCALE is the size of the Ni unit cell in angtroms.
#
calc AREA=2*NY*NZ*SCALE^2
write AREA
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#  From XMD output, take the difference in lattice energy and divide
#  the area of the free surface.  
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#  Note that the energy reported by the WRITE ENERGY command is the
#  lattice energy *per atom*.  Multiply by the number of atoms (in
#  this case, 256) to obtain the total lattice energy.  Then take
#  this lattice energy difference and divide by the surface
#  energy surface area to obtain the surface energy.
#
#
#  JR - 2 Nov 1998
#  (Thanks to Hengzhong Zhang <[e-mail]>)