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exercises_single_point_calculation_v2 [2015/02/06 13:42] – [Part II: Computation of the LJ energy curve] scleliaexercises:2015_ethz_mmm:single_point_calculation [2020/08/21 10:15] (current) – external edit 127.0.0.1
Line 142: Line 142:
          &NONBONDED             &NONBONDED   
           &LENNARD-JONES ! Lennard-Jones Xe parameters           &LENNARD-JONES ! Lennard-Jones Xe parameters
-           atoms Ne Ne +           atoms Xe Xe 
            EPSILON    [K_e] 232             EPSILON    [K_e] 232 
            SIGMA [angstrom]  3.98            SIGMA [angstrom]  3.98
Line 155: Line 155:
  
 === 4. Step === === 4. Step ===
-Here are reported the combiantion rules for pairs unlike pairs, i.e. for pairs of non identical atoms. \\ +Here are reported the combination rules for pairs unlike pairs, i.e. for pairs of non identical atoms. \\ 
 Once generated the ε and σ parameters for the couple Ar/Xe, generate once more the LJ dissociation curve. \\ Once generated the ε and σ parameters for the couple Ar/Xe, generate once more the LJ dissociation curve. \\
 Compare the "mixed" curve to the two "pure" curves and report the position and depth of the minimum. \\ Compare the "mixed" curve to the two "pure" curves and report the position and depth of the minimum. \\
Line 162: Line 162:
 $$ \epsilon_{ij}= \sqrt{\epsilon_i\epsilon_j}$$ $$ \epsilon_{ij}= \sqrt{\epsilon_i\epsilon_j}$$
  
 +<note tip>
 +Remember that you are running  with two different atom types. For this reason some of the input sections must be duplicated for the two kinds of atoms present
 +</note>
 +
 +  * The " LENNARD-JONES " section must be present for all the three possible couples: Ar-Ar, Xe-Xe and Xe-Ar.  Example: 
 +
 +<code>
 +      &LENNARD-JONES ! Lennard-Jones parameters for Ar-Ar interaction
 +          atoms Ar Ar
 +          EPSILON    [K_e] 119.8
 +          SIGMA [angstrom]  3.401
 +          RCUT  [angstrom]  25.0
 +      &END LENNARD-JONES
 +      &LENNARD-JONES ! Lennard-Jones Xe-Xe parameters
 +           atoms Xe Xe 
 +           EPSILON    [K_e] 232 
 +           SIGMA [angstrom]  3.98
 +           RCUT  [angstrom] 25.0
 +       &END LENNARD-JONES
 +      &LENNARD-JONES ! Lennard-Jones parameters for Ar-Xe interaction
 +          atoms Ar Xe
 +          EPSILON    [K_e] YOUR EPSILON
 +          SIGMA [angstrom]  YOUR SIGMA
 +          RCUT  [angstrom]  25.0
 +        &END LENNARD-JONES 
 +</code>
 +
 +  * The " CHARGE " section must be also duplicated: 
 +
 +<code>
 +         &CHARGE
 +          ATOM Xe
 +          CHARGE 0.0
 +         &END CHARGE
 +         &CHARGE
 +          ATOM Ar
 +          CHARGE 0.0
 +         &END CHARGE
 +         
 +</code>
 +
 +===== Questions =====
 +  * Sketch the LJ energy curve for the two set of parameters ($\sigma$ and $\epsilon$) provided. 
 +  * Report, for both curves, the minimum energy distance and the depth of the minimum.
 +  * What are the major differences between the curves? How do they relate to the sets of parameters provided?
  
exercises/2015_ethz_mmm/single_point_calculation.1423230130.txt.gz · Last modified: 2020/08/21 10:14 (external edit)