Added a LAMMPS ideal gas example

examples/clients/lammps/README.md

@@ -15,3 +15,5 @@
        reset args = none = reset electrostatics at each call
 
    Check a more detailed documentation at https://docs.lammps.org/fix_ipi.html
+
+`classical_md_gas` contains a basic setup in which LAMMPS does not compute any energy, and can be used to profile the overhead associated with i-PI communication, similar to what done in the `ipi_tests/profiling` folders using the built-in driver.

examples/clients/lammps/classical_md_gas/gas-4096.xyz

@@ -0,0 +1 @@
+../../../init_files/gas-4096.xyz

examples/clients/lammps/classical_md_gas/gas.lmp

@@ -0,0 +1,34 @@
+units		electron
+atom_style	atomic
+
+#pair_style	lj/cut/coul/long 17.01
+#pair_style      lj/cut/tip4p/long 1 2 1 1 0.278072379 17.007
+#bond_style      harmonic
+#bond_style      class2 
+#angle_style     harmonic
+#kspace_style	pppm 0.0001
+#kspace_style	pppm/tip4p 0.0001
+
+#read_data	data.lmp
+region          box block 0 10 0 10 0 10 units box
+create_box      1 box
+create_atoms    1 random 4096 123456 box
+mass 1 1.0
+
+
+timestep	0.00025
+
+#velocity all create 298.0 2345187
+
+#thermo_style	multi
+#thermo		1
+
+#fix		1 all nvt temp 298.0 298.0 30.0 tchain 1
+#fix 1 all nve
+fix 1 all ipi gas 32345 unix
+
+
+#dump		1 all xyz 25 dump.xyz
+
+run		100000000
+

examples/clients/lammps/classical_md_gas/input.xml

@@ -0,0 +1,35 @@
+<simulation verbosity='medium' threading='false' safe_stride='100'>
+    <ffsocket mode='unix' name='driver' pbc='false'>
+         <latency>  1.00000000e-04</latency>
+         <address> gas </address>
+         <exit_on_disconnect> False </exit_on_disconnect>
+   </ffsocket>
+   <total_steps>10000</total_steps>
+   <output prefix='simulation'>
+      <trajectory stride='1000' filename='pos'> positions </trajectory>
+      <properties stride='1000'> [ step, time, conserved, temperature, kinetic_md, potential, pressure_md, volume ] </properties>
+   </output>
+   <prng>
+      <seed>18885</seed>
+   </prng>
+   <system>
+      <forces> 
+          <force forcefield='driver'></force>
+      </forces>
+      <initialize nbeads='1'>
+        <file mode='xyz'> gas-4096.xyz</file>
+        <cell> [10.0, 0, 0, 0, 10.0, 0, 0, 0, 10.0] </cell>
+        <masses mode='manual'> [1.0] </masses>
+        <velocities mode='thermal'> 1 </velocities>
+      </initialize>
+      <ensemble>
+         <temperature> 1 </temperature>
+      </ensemble>
+      <motion mode='dynamics'>
+        <fixcom> False </fixcom>
+        <dynamics mode='nve'>
+            <timestep> 0.01 </timestep>
+        </dynamics>
+      </motion>
+  </system>
+</simulation>