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--- exercises_single_point_calculation_v2 [2015/02/06 13:24] – created sclelia
+++ exercises:2015_ethz_mmm:single_point_calculation [2020/08/21 10:15] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-====== Computation of the Lennard Jones curve for two Ar atoms ======
+====== Computation of the Lennard Jones curve ======
 In this exercise you will compute the Lennard-Jones energy curve for a system of two Ar atoms.\\
 In Part I you find the instructions for computing the energy of two Ar atoms at a distance $r=3.00 Å$.\\
 In Part II you find the instructions for getting the energy profile as a function of $r$.\\
-Additonal parameters for Kr and combination rules to obtain new parameters are provided in  Part III and IV.
+Additonal parameters for Xe and combination rules to obtain new parameters are provided in  Part III and IV.
 ===== Part I:  Single Point (Energy) calculation =====
@@ Line 137: / Line 137: @@
 === 3. Step ===
-Here are reported the LJ parameters for Kr atoms. Those are to replace the Ar parameters in the input file, along with your Kr coordinates that have to replace the Ar coordinates. A new LJ curve for Kr atoms can be now generated.
+Here are reported the LJ parameters for Xe atoms. Those are to replace the Ar parameters in the input file, along with your Xe coordinates that have to replace the Ar coordinates. A new LJ curve for Xe atoms can be now generated.
 <code>
          &NONBONDED
-          &LENNARD-JONES ! Lennard-Jones Ne parameters
+          &LENNARD-JONES ! Lennard-Jones Xe parameters
-           atoms Ne Ne
+           atoms Xe Xe
-           EPSILON    [K_e] 163
+           EPSILON    [K_e] 232
-           SIGMA [angstrom]  3.65
+           SIGMA [angstrom]  3.98
            RCUT  [angstrom] 25.0
           &END LENNARD-JONES
          &END NONBONDED
          &CHARGE
-          ATOM Ne
+          ATOM Xe
           CHARGE 0.0
          &END CHARGE
@@ Line 155: / Line 155: @@
 === 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/Kr, 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. \\
@@ Line 162: / Line 162: @@
 $$ \epsilon_{ij}= \sqrt{\epsilon_i\epsilon_j}$$
+<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?