diff --git a/gromacs/force_lj.c b/gromacs/force_lj.c
index 00d35ce..ca280ea 100644
--- a/gromacs/force_lj.c
+++ b/gromacs/force_lj.c
@@ -45,7 +45,7 @@ static inline void gmx_load_simd_4xn_interactions(
 double computeForceLJ_ref(Parameter *param, Atom *atom, Neighbor *neighbor, Stats *stats) {
     DEBUG_MESSAGE("computeForceLJ begin\n");
     int Nlocal = atom->Nlocal;
-    NeighborCluster* neighs;
+    int *neighs;
     MD_FLOAT cutforcesq = param->cutforce * param->cutforce;
     MD_FLOAT sigma6 = param->sigma6;
     MD_FLOAT epsilon = param->epsilon;
@@ -77,7 +77,7 @@ double computeForceLJ_ref(Parameter *param, Atom *atom, Neighbor *neighbor, Stat
         int numneighs = neighbor->numneigh[ci];
 
         for(int k = 0; k < numneighs; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
             int any = 0;
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
@@ -158,7 +158,7 @@ double computeForceLJ_ref(Parameter *param, Atom *atom, Neighbor *neighbor, Stat
 double computeForceLJ_2xnn_half(Parameter *param, Atom *atom, Neighbor *neighbor, Stats *stats) {
     DEBUG_MESSAGE("computeForceLJ_2xnn begin\n");
     int Nlocal = atom->Nlocal;
-    NeighborCluster* neighs;
+    int *neighs;
     MD_FLOAT cutforcesq = param->cutforce * param->cutforce;
     MD_FLOAT sigma6 = param->sigma6;
     MD_FLOAT epsilon = param->epsilon;
@@ -240,9 +240,9 @@ double computeForceLJ_2xnn_half(Parameter *param, Atom *atom, Neighbor *neighbor
         MD_SIMD_FLOAT fiz2 = simd_zero();
 
         for(int k = 0; k < numneighs_masked; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
-            //int imask = neighs[k].imask;
+            //int imask = neighs_imask[k];
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
             MD_FLOAT *cj_f = &atom->cl_f[cj_vec_base];
             //MD_SIMD_MASK interact0;
@@ -331,7 +331,7 @@ double computeForceLJ_2xnn_half(Parameter *param, Atom *atom, Neighbor *neighbor
         }
 
         for(int k = numneighs_masked; k < numneighs; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
             MD_FLOAT *cj_f = &atom->cl_f[cj_vec_base];
@@ -401,7 +401,7 @@ double computeForceLJ_2xnn_half(Parameter *param, Atom *atom, Neighbor *neighbor
 double computeForceLJ_2xnn_full(Parameter *param, Atom *atom, Neighbor *neighbor, Stats *stats) {
     DEBUG_MESSAGE("computeForceLJ_2xnn begin\n");
     int Nlocal = atom->Nlocal;
-    NeighborCluster* neighs;
+    int *neighs;
     MD_FLOAT cutforcesq = param->cutforce * param->cutforce;
     MD_FLOAT sigma6 = param->sigma6;
     MD_FLOAT epsilon = param->epsilon;
@@ -454,9 +454,8 @@ double computeForceLJ_2xnn_full(Parameter *param, Atom *atom, Neighbor *neighbor
         MD_SIMD_FLOAT fiz2 = simd_zero();
 
         for(int k = 0; k < numneighs_masked; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
-            int imask = neighs[k].imask;
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
             unsigned int mask0, mask1, mask2, mask3;
 
@@ -507,7 +506,7 @@ double computeForceLJ_2xnn_full(Parameter *param, Atom *atom, Neighbor *neighbor
         }
 
         for(int k = numneighs_masked; k < numneighs; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
 
@@ -570,7 +569,7 @@ double computeForceLJ_2xnn(Parameter *param, Atom *atom, Neighbor *neighbor, Sta
 double computeForceLJ_4xn_half(Parameter *param, Atom *atom, Neighbor *neighbor, Stats *stats) {
     DEBUG_MESSAGE("computeForceLJ_4xn begin\n");
     int Nlocal = atom->Nlocal;
-    NeighborCluster* neighs;
+    int *neighs;
     MD_FLOAT cutforcesq = param->cutforce * param->cutforce;
     MD_FLOAT sigma6 = param->sigma6;
     MD_FLOAT epsilon = param->epsilon;
@@ -635,9 +634,8 @@ double computeForceLJ_4xn_half(Parameter *param, Atom *atom, Neighbor *neighbor,
         MD_SIMD_FLOAT fiz3 = simd_zero();
 
         for(int k = 0; k < numneighs_masked; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
-            int imask = neighs[k].imask;
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
             MD_FLOAT *cj_f = &atom->cl_f[cj_vec_base];
             MD_SIMD_FLOAT xj_tmp = simd_load(&cj_x[CL_X_OFFSET]);
@@ -741,9 +739,8 @@ double computeForceLJ_4xn_half(Parameter *param, Atom *atom, Neighbor *neighbor,
         }
 
         for(int k = numneighs_masked; k < numneighs; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
-            int imask = neighs[k].imask;
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
             MD_FLOAT *cj_f = &atom->cl_f[cj_vec_base];
             MD_SIMD_FLOAT xj_tmp = simd_load(&cj_x[CL_X_OFFSET]);
@@ -846,7 +843,7 @@ double computeForceLJ_4xn_half(Parameter *param, Atom *atom, Neighbor *neighbor,
 double computeForceLJ_4xn_full(Parameter *param, Atom *atom, Neighbor *neighbor, Stats *stats) {
     DEBUG_MESSAGE("computeForceLJ_4xn begin\n");
     int Nlocal = atom->Nlocal;
-    NeighborCluster* neighs;
+    int *neighs;
     MD_FLOAT cutforcesq = param->cutforce * param->cutforce;
     MD_FLOAT sigma6 = param->sigma6;
     MD_FLOAT epsilon = param->epsilon;
@@ -911,9 +908,8 @@ double computeForceLJ_4xn_full(Parameter *param, Atom *atom, Neighbor *neighbor,
         MD_SIMD_FLOAT fiz3 = simd_zero();
 
         for(int k = 0; k < numneighs_masked; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
-            int imask = neighs[k].imask;
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
             MD_SIMD_FLOAT xj_tmp = simd_load(&cj_x[CL_X_OFFSET]);
             MD_SIMD_FLOAT yj_tmp = simd_load(&cj_x[CL_Y_OFFSET]);
@@ -991,9 +987,8 @@ double computeForceLJ_4xn_full(Parameter *param, Atom *atom, Neighbor *neighbor,
         }
 
         for(int k = numneighs_masked; k < numneighs; k++) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             int cj_vec_base = CJ_VECTOR_BASE_INDEX(cj);
-            int imask = neighs[k].imask;
             MD_FLOAT *cj_x = &atom->cl_x[cj_vec_base];
             MD_SIMD_FLOAT xj_tmp = simd_load(&cj_x[CL_X_OFFSET]);
             MD_SIMD_FLOAT yj_tmp = simd_load(&cj_x[CL_Y_OFFSET]);
diff --git a/gromacs/includes/neighbor.h b/gromacs/includes/neighbor.h
index 6d3de64..668edc8 100644
--- a/gromacs/includes/neighbor.h
+++ b/gromacs/includes/neighbor.h
@@ -25,11 +25,6 @@
 #define NBNXN_INTERACTION_MASK_DIAG_J8_0 0xf0f8fcfeU
 #define NBNXN_INTERACTION_MASK_DIAG_J8_1 0x0080c0e0U
 
-typedef struct {
-    int cj;
-    unsigned int imask;
-} NeighborCluster;
-
 typedef struct {
     int every;
     int ncalls;
@@ -37,7 +32,8 @@ typedef struct {
     int* numneigh;
     int* numneigh_masked;
     int half_neigh;
-    NeighborCluster* neighbors;
+    int* neighbors;
+    unsigned int* neighbors_imask;
 } Neighbor;
 
 extern void initNeighbor(Neighbor*, Parameter*);
diff --git a/gromacs/main-stub.c b/gromacs/main-stub.c
index a4dbfd3..3cd8431 100644
--- a/gromacs/main-stub.c
+++ b/gromacs/main-stub.c
@@ -72,7 +72,8 @@ void createNeighbors(Atom *atom, Neighbor *neighbor, int pattern, int nneighs, i
     const int ncj = atom->Nclusters_local / jfac;
     const unsigned int imask = NBNXN_INTERACTION_MASK_ALL;
     neighbor->numneigh = (int*) malloc(atom->Nclusters_max * sizeof(int));
-    neighbor->neighbors = (NeighborCluster*) malloc(atom->Nclusters_max * maxneighs * sizeof(int));
+    neighbor->neighbors = (int*) malloc(atom->Nclusters_max * maxneighs * sizeof(int));
+    neighbor->neighbors_imask = (unsigned int*) malloc(atom->Nclusters_max * maxneighs * sizeof(unsigned int));
 
     if(pattern == P_RAND && ncj <= nneighs) {
         fprintf(stderr, "Error: P_RAND: Number of j-clusters should be higher than number of j-cluster neighbors per i-cluster!\n");
@@ -80,7 +81,8 @@ void createNeighbors(Atom *atom, Neighbor *neighbor, int pattern, int nneighs, i
     }
 
     for(int ci = 0; ci < atom->Nclusters_local; ci++) {
-        NeighborCluster *neighptr = &(neighbor->neighbors[ci * neighbor->maxneighs]);
+        int *neighptr = &(neighbor->neighbors[ci * neighbor->maxneighs]);
+        unsigned int *neighptr_imask = &(neighbor->neighbors_imask[ci * neighbor->maxneighs]);
         int j = (pattern == P_SEQ) ? CJ0_FROM_CI(ci) : 0;
         int m = (pattern == P_SEQ) ? ncj : nneighs;
         int k = 0;
@@ -90,26 +92,26 @@ void createNeighbors(Atom *atom, Neighbor *neighbor, int pattern, int nneighs, i
                 int found = 0;
                 do {
                     int cj = rand() % ncj;
-                    neighptr[k].cj = cj;
-                    neighptr[k].imask = imask;
+                    neighptr[k] = cj;
+                    neighptr_imask[k] = imask;
                     found = 0;
                     for(int l = 0; l < k; l++) {
-                        if(neighptr[l].cj == cj) {
+                        if(neighptr[l] == cj) {
                             found = 1;
                         }
                     }
                 } while(found == 1);
             } else {
-                neighptr[k].cj = j;
-                neighptr[k].imask = imask;
+                neighptr[k] = j;
+                neighptr_imask[k] = imask;
                 j = (j + 1) % m;
             }
         }
 
         for(int r = 1; r < nreps; r++) {
             for(int k = 0; k < nneighs; k++) {
-                neighptr[r * nneighs + k].cj = neighptr[k].cj;
-                neighptr[r * nneighs + k].imask = neighptr[k].imask;
+                neighptr[r * nneighs + k] = neighptr[k];
+                neighptr_imask[r * nneighs + k] = neighptr_imask[k];
             }
         }
 
diff --git a/gromacs/neighbor.c b/gromacs/neighbor.c
index 6f627bd..dfba8f5 100644
--- a/gromacs/neighbor.c
+++ b/gromacs/neighbor.c
@@ -232,7 +232,8 @@ void buildNeighbor(Atom *atom, Neighbor *neighbor) {
         if(neighbor->neighbors) free(neighbor->neighbors);
         neighbor->numneigh = (int*) malloc(nmax * sizeof(int));
         neighbor->numneigh_masked = (int*) malloc(nmax * sizeof(int));
-        neighbor->neighbors = (NeighborCluster*) malloc(nmax * neighbor->maxneighs * sizeof(NeighborCluster));
+        neighbor->neighbors = (int*) malloc(nmax * neighbor->maxneighs * sizeof(int));
+        neighbor->neighbors_imask = (unsigned int*) malloc(nmax * neighbor->maxneighs * sizeof(unsigned int));
     }
 
     MD_FLOAT bbx = 0.5 * (binsizex + binsizex);
@@ -248,7 +249,8 @@ void buildNeighbor(Atom *atom, Neighbor *neighbor) {
 
         for(int ci = 0; ci < atom->Nclusters_local; ci++) {
             int ci_cj1 = CJ1_FROM_CI(ci);
-            NeighborCluster *neighptr = &(neighbor->neighbors[ci * neighbor->maxneighs]);
+            int *neighptr = &(neighbor->neighbors[ci * neighbor->maxneighs]);
+            unsigned int *neighptr_imask = &(neighbor->neighbors_imask[ci * neighbor->maxneighs]);
             int n = 0, nmasked = 0;
             int ibin = atom->icluster_bin[ci];
             MD_FLOAT ibb_xmin = atom->iclusters[ci].bbminx;
@@ -325,13 +327,13 @@ void buildNeighbor(Atom *atom, Neighbor *neighbor) {
                                     #endif
 
                                     if(imask == NBNXN_INTERACTION_MASK_ALL) {
-                                        neighptr[n].cj = cj;
-                                        neighptr[n].imask = imask;
+                                        neighptr[n] = cj;
+                                        neighptr_imask[n] = imask;
                                     } else {
-                                        neighptr[n].cj = neighptr[nmasked].cj;
-                                        neighptr[n].imask = neighptr[nmasked].imask;
-                                        neighptr[nmasked].cj = cj;
-                                        neighptr[nmasked].imask = imask;
+                                        neighptr[n] = neighptr[nmasked];
+                                        neighptr_imask[n] = neighptr_imask[nmasked];
+                                        neighptr[nmasked] = cj;
+                                        neighptr_imask[nmasked] = imask;
                                         nmasked++;
                                     }
 
@@ -357,8 +359,8 @@ void buildNeighbor(Atom *atom, Neighbor *neighbor) {
             // Fill neighbor list with dummy values to fit vector width
             if(CLUSTER_N < VECTOR_WIDTH) {
                 while(n % (VECTOR_WIDTH / CLUSTER_N)) {
-                    neighptr[n].cj = atom->dummy_cj; // Last cluster is always a dummy cluster
-                    neighptr[n].imask = 0;
+                    neighptr[n] = atom->dummy_cj; // Last cluster is always a dummy cluster
+                    neighptr_imask[n] = 0;
                     n++;
                 }
             }
@@ -378,7 +380,8 @@ void buildNeighbor(Atom *atom, Neighbor *neighbor) {
             fprintf(stdout, "RESIZE %d\n", neighbor->maxneighs);
             neighbor->maxneighs = new_maxneighs * 1.2;
             free(neighbor->neighbors);
-            neighbor->neighbors = (NeighborCluster*) malloc(atom->Nmax * neighbor->maxneighs * sizeof(int));
+            neighbor->neighbors = (int *) malloc(atom->Nmax * neighbor->maxneighs * sizeof(int));
+            neighbor->neighbors_imask = (unsigned int *) malloc(atom->Nmax * neighbor->maxneighs * sizeof(unsigned int));
         }
     }
 
@@ -433,20 +436,21 @@ void pruneNeighbor(Parameter *param, Atom *atom, Neighbor *neighbor) {
     MD_FLOAT cutsq = cutneighsq;
 
     for(int ci = 0; ci < atom->Nclusters_local; ci++) {
-        NeighborCluster *neighs = &neighbor->neighbors[ci * neighbor->maxneighs];
+        int *neighs = &neighbor->neighbors[ci * neighbor->maxneighs];
+        unsigned int *neighs_imask = &neighbor->neighbors_imask[ci * neighbor->maxneighs];
         int numneighs = neighbor->numneigh[ci];
         int numneighs_masked = neighbor->numneigh_masked[ci];
         int k = 0;
 
         // Remove dummy clusters if necessary
         if(CLUSTER_N < VECTOR_WIDTH) {
-            while(neighs[numneighs - 1].cj == atom->dummy_cj) {
+            while(neighs[numneighs - 1] == atom->dummy_cj) {
                 numneighs--;
             }
         }
 
         while(k < numneighs) {
-            int cj = neighs[k].cj;
+            int cj = neighs[k];
             if(atomDistanceInRange(atom, ci, cj, cutsq)) {
                 k++;
             } else {
@@ -461,8 +465,8 @@ void pruneNeighbor(Parameter *param, Atom *atom, Neighbor *neighbor) {
         // Readd dummy clusters if necessary
         if(CLUSTER_N < VECTOR_WIDTH) {
             while(numneighs % (VECTOR_WIDTH / CLUSTER_N)) {
-                neighs[numneighs].cj = atom->dummy_cj; // Last cluster is always a dummy cluster
-                neighs[numneighs].imask = 0;
+                neighs[numneighs] = atom->dummy_cj; // Last cluster is always a dummy cluster
+                neighs_imask[numneighs] = 0;
                 numneighs++;
             }
         }
diff --git a/gromacs/tracing.c b/gromacs/tracing.c
index c87b73d..efa284e 100644
--- a/gromacs/tracing.c
+++ b/gromacs/tracing.c
@@ -13,7 +13,8 @@ void traceAddresses(Parameter *param, Atom *atom, Neighbor *neighbor, int timest
     MEM_TRACER_INIT;
     INDEX_TRACER_INIT;
     int Nlocal = atom->Nlocal;
-    NeighborCluster* neighs;
+    int *neighs;
+    unsigned int *neighs_imask;
     //MD_FLOAT* fx = atom->fx; MD_FLOAT* fy = atom->fy; MD_FLOAT* fz = atom->fz;
 
     INDEX_TRACE_NATOMS(Nlocal, atom->Nghost, neighbor->maxneighs);
@@ -34,7 +35,7 @@ void traceAddresses(Parameter *param, Atom *atom, Neighbor *neighbor, int timest
         DIST_TRACE(neighs, numneighs);
 
         for(int k = 0; k < numneighs; k++) {
-            int j = neighs[k].cj;
+            int j = neighs[k];
             MEM_TRACE(j, 'R');
             MEM_TRACE(atom_x(j), 'R');
             MEM_TRACE(atom_y(j), 'R');