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+====== Geometry Optimization ======
+In this exercise you will run a geometry optimization calculation, for two Kr atoms placed at distance $r=3.00Å$.
+=== 1. Step ===
+Save the following commented CP2K input file to a file named ''geopt.inp''
+<code - geopt.inp>
+&GLOBAL
+   RUN_TYPE GEO_OPT
+   PROJECT_NAME geopt  ! the calculation will produce a few output files, that will be labeled with this name
+&END GLOBAL
+&FORCE_EVAL
+  METHOD FIST
+  &MM
+    &FORCEFIELD
+        &SPLINE
+          EMAX_SPLINE 10000    ! numeric parameter to ensure calculation stability. Should not be changed
+        &END
+        &NONBONDED
+          &LENNARD-JONES
+          atoms Kr Kr
+          EPSILON    [K_e] 164.56
+          SIGMA [angstrom]   3.601
+          RCUT  [angstrom]  25.0
+        &END LENNARD-JONES
+      &END NONBONDED
+      &CHARGE
+        ATOM Kr
+        CHARGE 0.0
+      &END CHARGE
+    &END FORCEFIELD
+    &POISSON
+     PERIODIC NONE
+      &EWALD
+        EWALD_TYPE none
+      &END EWALD
+    &END POISSON
+  &END MM
+  &SUBSYS
+   &CELL
+    ABC [angstrom] 10 10 10
+      PERIODIC NONE
+   &END CELL
+   &COORD
+    UNIT angstrom
+    Kr  0 0 0
+    Kr  3 0 0
+   &END COORD
+  &END SUBSYS
+&END FORCE_EVAL
+</code>
+=== 2. Step: Run CP2K ===
+<code>
+$ cp2k.popt -i geopt.inp -o geopt.out
+</code>
+=== 3. Step ===
+For the GEO_OPT calculations, CP2k produces a few output files. The most important are:
+  * geopt.out: standard CP2K output file. It tells you whether that the calculation is completed and what is the energy of the final configuration.
+  * geopt-pos-1.xyz : optimization trajectory. You can open it with VMD.
+=== 4. Step: Checking the optimization trajectory ===
+<code>
+$ vmd  geopt-pos-1.xyz
+</code>
+<note tip>
+If VMD started up properly but the viewer window remains empty, try the following:
+  - Open the menu item //Graphics// -> //Representations...//
+  - In the appearing dialog set the //Drawing Methods// to //VDW// and the //Sphere Scale// to 0.2 .
+</note>
+=== 5. Step: Checking the energy ===
+In the geopt.out file you have a list of energies, one for each geometry optimization step that was performed. The overall energy should decrease, until the minimum.
+To check it, you can simply search the geopt.out file with the ''grep'' command:
+<code>
+$  grep ENERGY  geopt.out  | awk '{print $9}'
+</code>
+The energy at each step will be printed on screen.
+=== 6. Step ===
+Run the input for different starting distances, and check whether the simulation always find the minimal energy configuration.
+===== Questions =====
+  * After running geometry optimization (on one set of parameters, starting from different distances), do you always find the minimum energy distance?
+  * If not, report the distances at which the geometry optimization does not bring the system in the minimum energy configuration.