This folder contains the data we obtained for our paper "Hydroxylation-driven surface reconstruction at the origin of compressive-to-tensile stress transition in metal oxide nanoparticles". 
Folder adsorb: this folder contains the information on calculating the adsorption energy of one water monomer on different surfaces of MgO. There are three subfolders, 100, 110 and 111. Within each subfolder, there are files dump_L.txt which contains the structure of a specific surface with one water molecule on the top surface and one water molecule on the bottom surface. For the {111} surface, one OH group is introduced to the Mg-terminated surface and one H is introduced to the O-terminated surface, so in total one water molecule is introduced. File in.relax which is the input file for MS simulations to structurally relax the surfaces with the water molecule.
Folder water: file water is the initial structure of a water monomer in vacuum. File in.relax is used for structurally relaxing the initial water structure. Folder no_d3 contains the same in.relax file just with the potential for simulations without D3 corrections.
Folder mgo_bulk: there are two folders inside this folder. Folder lattice parameter: contains file in.relax used for structurally relax the bulk MgO and output the relation between lattice size and pressure. File mgo.dat is the initial structure of MgO downloaded from Materials Project. Files bulk_pe_d3.dat and bulk_pe_nod3.dat are the results for simulations with and without D3 corrections, respectively. Folder elastic_constant: contains files in.elastic, displace.mod, init.mod and potential.mod which are used for calculating the elastic constants of MgO.
Folder mgoh_bulk: there are two folders inside this folder. Folder lattice parameter: contains file in.relax used for structurally relax the bulk MgOH and output the relation between lattice size and pressure. File mgoh.dat is the initial structure of MgOH downloaded from Materials Project. Files bulk_pe_d3.dat and bulk_pe_nod3.dat are the results for simulations with and without D3 corrections, respectively. Folder elastic_constant: contains files in.elastic, displace.mod, init.mod and potential.mod which are used for calculating the elastic constants of MgOH.
Folder 100: file mgo100.lmp is the unit cell of MgO with z-axis perpendicular to the {100} plane. There are three folders inside this folder, folders thick, vac, water. 
Folder thick: contains the input files (in.relax.*) for calculating surface energies for samples with different thickness and the results (surf_*pe.dat) of surface energies vs. biaxial strains for each sample.  
The input files should be used in the following sequence: 
1. in.relax.0: create {100} surfaces with different separations between the top and bottom surfaces, and relax the structure. The bulk lattice constant of MgO obtained from mgo_bulk is used to create the surfaces and no box relaxation along x and y-axis is allowed. 
2. in.relax.1: scale the box along z-axis to find the box dimension along z-axis which ensures 0 pressure along the z-axis. After this step is done, one can use the codes in the Jupyter notebook "analysis.ipynb" (third cell) to output the z-dimension in a text file called "surf_z.txt".
3. in.relax.2: create the bulk region for surface energy calculations, the bulk regions should have the same x and y-dimensions as the surfaces, and z-axis is scaled to find the z-dimension which ensures 0 pressure along the z-axis. After this step is done, one can use the codes in the Jupyter notebook "analysis.ipynb" (fourth cell) to output the z-dimension in a text file called "mgo_z.txt".
4. in.relax1: Calculate the surface energies. Within this step, files surf_z.txt and mgo_z.txt need to be used to get the optimal z-dimensions for the bulk and surface. 
5. in.relax2: apply biaxial strains to surfaces and scale the box along the z-axis to find the z-dimension which ensures 0 pressure along the z-axis.
6. in.relax.2.1: apply biaxial strains to bulks and scale the box along the z-axis to find the z-dimension which ensures 0 pressure along the z-axis. After the fifth and sixth steps are done, one can use the codes in the Jupyter notebook "analysis.ipynb" (fifth cell) to output the z-dimensions in text files called "surf*_a_pe.dat" and "mgo*_a_pe.dat".
7. in.relax3: Calculate the surface energies at each applied strain. Within this step, files "surf*_a_pe.dat" and "mgo*_a_pe.dat" need to be used to get the optimal z-dimensions for the bulk and surface.
Folder vac: contains the input files (in.relax.*) for calculating surface energies for samples with different vacuum layer thickness and the results (surf_*pe.dat) of surface energies vs. biaxial strains for each sample. In these simulations, the distances between top and bottom surfaces are the same (~10 nm). The input files should be used in the same sequence as mentioned above.
Folder water: contains the input files (in.relax.*) for calculating surface energies for samples with different # of water molecules on the surface and the results (surf_*pe.dat) of surface energies vs. biaxial strains for each sample. dump_*.txt files are the initial structures of surfaces with different # of water molecules. In these simulations, the distances between top and bottom surfaces are the same (~10 nm). The input files should be used in the same sequence as mentioned above.
Folder 110: file mgo110.lmp is the unit cell of MgO with z-axis perpendicular to the {110} plane. There are three folders inside this folder, folders thick, vac, water. The input files and output data in each folder are the same as those in folder 100.
Folder 111: file mgo111.lmp is the unit cell of MgO with z-axis perpendicular to the {111} plane. There are three folders inside this folder, folders thick, vac, water. The input files and output data in each folder are the same as those in folder 100.
analysis.ipynb: python codes used during MD simulations and post MD simulations.
Adsorb_en.xlsx: excel spreadsheet contains the adsorption energies of one water monomer on {100}, {110} and {111} surfaces. The results obtained by simulations with and without D3 corrections are shown.