diff --git a/src/trexio.c b/src/trexio.c
index 042ddb3..554d46f 100644
--- a/src/trexio.c
+++ b/src/trexio.c
@@ -245,16 +245,13 @@ trexio_exit_code trexio_read_nucleus_coord(trexio_t* file, double* coord) {
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_coord = nucleus_num*3;
-  if (dim_coord < 0) return TREXIO_FAILURE;
-
   uint32_t rank = 2;
   uint64_t dims[2] = {nucleus_num, 3}; 
 
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_read_nucleus_coord(file, coord, (uint64_t) dim_coord);
+    return trexio_text_read_nucleus_coord(file, coord, rank, dims);
     break;
 
   case TREXIO_HDF5:
@@ -278,16 +275,13 @@ trexio_exit_code trexio_write_nucleus_coord(trexio_t* file, const double* coord)
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_coord = nucleus_num*3;
-  if (dim_coord < 0) return TREXIO_FAILURE;
-
   uint32_t rank = 2;
   uint64_t dims[2] = {nucleus_num, 3};
  
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_write_nucleus_coord(file, coord, (uint64_t) dim_coord);
+    return trexio_text_write_nucleus_coord(file, coord, rank, dims);
     break;
 
   case TREXIO_HDF5:
@@ -311,13 +305,13 @@ trexio_exit_code trexio_read_nucleus_charge(trexio_t* file, double* charge) {
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_charge = nucleus_num;
-  if (dim_charge < 0) return TREXIO_FAILURE;
+  uint32_t rank = 1;
+  uint64_t dims[1] = {nucleus_num}; 
 
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_read_nucleus_charge(file, charge, (uint64_t) dim_charge);
+    return trexio_text_read_nucleus_charge(file, charge, rank, dims);
     break;
 /*
   case TREXIO_HDF5:
@@ -341,13 +335,13 @@ trexio_exit_code trexio_write_nucleus_charge(trexio_t* file, const double* charg
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_charge = nucleus_num;
-  if (dim_charge < 0) return TREXIO_FAILURE;
+  uint32_t rank = 1;
+  uint64_t dims[1] = {nucleus_num}; 
 
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_write_nucleus_charge(file, charge, (uint64_t) dim_charge);
+    return trexio_text_write_nucleus_charge(file, charge, rank, dims);
     break;
 /*
   case TREXIO_HDF5:
diff --git a/src/trexio.org b/src/trexio.org
index 874585f..3b58cf2 100644
--- a/src/trexio.org
+++ b/src/trexio.org
@@ -410,16 +410,13 @@ trexio_exit_code trexio_read_nucleus_coord(trexio_t* file, double* coord) {
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_coord = nucleus_num*3;
-  if (dim_coord < 0) return TREXIO_FAILURE;
-
   uint32_t rank = 2;
   uint64_t dims[2] = {nucleus_num, 3}; 
 
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_read_nucleus_coord(file, coord, (uint64_t) dim_coord);
+    return trexio_text_read_nucleus_coord(file, coord, rank, dims);
     break;
 
   case TREXIO_HDF5:
@@ -443,16 +440,13 @@ trexio_exit_code trexio_write_nucleus_coord(trexio_t* file, const double* coord)
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_coord = nucleus_num*3;
-  if (dim_coord < 0) return TREXIO_FAILURE;
-
   uint32_t rank = 2;
   uint64_t dims[2] = {nucleus_num, 3};
  
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_write_nucleus_coord(file, coord, (uint64_t) dim_coord);
+    return trexio_text_write_nucleus_coord(file, coord, rank, dims);
     break;
 
   case TREXIO_HDF5:
@@ -484,13 +478,13 @@ trexio_exit_code trexio_read_nucleus_charge(trexio_t* file, double* charge) {
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_charge = nucleus_num;
-  if (dim_charge < 0) return TREXIO_FAILURE;
+  uint32_t rank = 1;
+  uint64_t dims[1] = {nucleus_num}; 
 
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_read_nucleus_charge(file, charge, (uint64_t) dim_charge);
+    return trexio_text_read_nucleus_charge(file, charge, rank, dims);
     break;
 /*
   case TREXIO_HDF5:
@@ -514,13 +508,13 @@ trexio_exit_code trexio_write_nucleus_charge(trexio_t* file, const double* charg
   trexio_exit_code rc = trexio_read_nucleus_num(file, &nucleus_num);
   if (rc != TREXIO_SUCCESS) return rc;
 
-  int64_t dim_charge = nucleus_num;
-  if (dim_charge < 0) return TREXIO_FAILURE;
+  uint32_t rank = 1;
+  uint64_t dims[1] = {nucleus_num}; 
 
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_write_nucleus_charge(file, charge, (uint64_t) dim_charge);
+    return trexio_text_write_nucleus_charge(file, charge, rank, dims);
     break;
 /*
   case TREXIO_HDF5:
diff --git a/src/trexio_text.c b/src/trexio_text.c
index 3dd4529..6bd36c9 100644
--- a/src/trexio_text.c
+++ b/src/trexio_text.c
@@ -108,7 +108,9 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
   nucleus->file     = NULL;
   nucleus->num      = 0;
   nucleus->coord    = NULL;
+  nucleus->dims_coord = NULL;
   nucleus->charge   = NULL;
+  nucleus->dims_charge = NULL;
   nucleus->to_flush = 0;
 
   /* Try to open the file. If the file does not exist, return */
@@ -134,23 +136,55 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
     int rc;
     rc = fscanf(f, "%s", buffer);
     assert (rc == 1);
-    assert (strcmp(buffer, "dim_charge") == 0);
+    assert (strcmp(buffer, "rank_charge") == 0);
     
-    rc = fscanf(f, "%lu", &(nucleus->dim_charge));
+    rc = fscanf(f, "%u", &(nucleus->rank_charge));
     assert (rc == 1);
+     
+    nucleus->dims_charge = (uint64_t*) calloc(nucleus->rank_charge, sizeof(uint64_t));
+    assert (nucleus->dims_charge != NULL);
+    
+    uint64_t size_charge = 1;
+    for (uint i=0; i<nucleus->rank_charge; i++){
+
+      rc = fscanf(f, "%s", buffer);
+      assert (rc == 1);
+      //assert (strcmp(buffer, "dims_charge") == 0);
+    
+      rc = fscanf(f, "%lu", &(nucleus->dims_charge[i]));
+      assert (rc == 1);
+
+      size_charge *= nucleus->dims_charge[i];
+    }
     
     rc = fscanf(f, "%s", buffer);
     assert (rc == 1);
-    assert (strcmp(buffer, "dim_coord") == 0);
+    assert (strcmp(buffer, "rank_coord") == 0);
     
-    rc = fscanf(f, "%lu", &(nucleus->dim_coord));
+    rc = fscanf(f, "%u", &(nucleus->rank_coord));
     assert (rc == 1);
+     
+    nucleus->dims_coord = (uint64_t*) calloc(nucleus->rank_coord, sizeof(uint64_t));
+    assert (nucleus->dims_coord != NULL);
+    
+    uint64_t size_coord = 1;
+    for (uint i=0; i<nucleus->rank_coord; i++){
+
+      rc = fscanf(f, "%s", buffer);
+      assert (rc == 1);
+      //assert (strcmp(buffer, "dims_coord") == 0);
+    
+      rc = fscanf(f, "%lu", &(nucleus->dims_coord[i]));
+      assert (rc == 1);
+
+      size_coord *= nucleus->dims_coord[i];
+    }
     
     /* Allocate arrays */
-    nucleus->charge = (double*) calloc(nucleus->dim_charge, sizeof(double));
+    nucleus->charge = (double*) calloc(size_charge, sizeof(double));
     assert (nucleus->charge != NULL);
     
-    nucleus->coord = (double*) calloc(nucleus->dim_coord, sizeof(double));
+    nucleus->coord = (double*) calloc(size_coord, sizeof(double));
     assert (nucleus->coord != NULL);
     
     /* Read data */
@@ -165,7 +199,7 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
     assert (rc == 1);
     assert (strcmp(buffer, "charge") == 0);
     
-    for (uint64_t i=0 ; i<nucleus->dim_charge ; i++) {
+    for (uint64_t i=0 ; i<size_charge ; i++) {
       rc = fscanf(f, "%lf", &(nucleus->charge[i]));
       assert (rc == 1);
     }
@@ -174,7 +208,7 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
     assert (rc == 1);
     assert (strcmp(buffer, "coord") == 0);
     
-    for (uint64_t i=0 ; i<nucleus->dim_coord ; i++) {
+    for (uint64_t i=0 ; i<size_coord ; i++) {
       rc = fscanf(f, "%lf", &(nucleus->coord[i]));
       assert (rc == 1);
     }
@@ -207,19 +241,32 @@ trexio_exit_code trexio_text_flush_nucleus(const trexio_text_t* file) {
   assert (f != NULL);
   rewind(f);
 
-  /* Write the dimensioning variables */
-  fprintf(f, "dim_charge %ld\n", nucleus->dim_charge);
-  fprintf(f, "dim_coord  %ld\n", nucleus->dim_coord );
+  /* Write the dimensioning variables */ 
+  fprintf(f, "rank_charge %d\n", nucleus->rank_charge);
+
+  uint64_t size_charge = 1;
+  for (uint i=0; i<nucleus->rank_charge; i++){
+    fprintf(f, "dims_charge[%d] %ld\n", i, nucleus->dims_charge[i]);
+    size_charge *= nucleus->dims_charge[i];
+  } 
+
+  fprintf(f, "rank_coord %d\n", nucleus->rank_coord);
+
+  uint64_t size_coord = 1;
+  for (uint i=0; i<nucleus->rank_coord; i++){
+    fprintf(f, "dims_coord[%d] %ld\n", i, nucleus->dims_coord[i]);
+    size_coord *= nucleus->dims_coord[i];
+  } 
 
   /* Write arrays */
   fprintf(f, "num %ld\n", nucleus->num);
   fprintf(f, "charge\n");
-  for (uint64_t i=0 ; i<nucleus->dim_charge ; i++) {
+  for (uint64_t i=0 ; i<size_charge ; i++) {
     fprintf(f, "%lf\n", nucleus->charge[i]);
   }
 
   fprintf(f, "coord\n");
-  for (uint64_t i=0 ; i<nucleus->dim_coord ; i++) {
+  for (uint64_t i=0 ; i<size_coord ; i++) {
       fprintf(f, "%lf\n", nucleus->coord[i]);
   }
   fflush(f);
@@ -245,11 +292,21 @@ trexio_exit_code trexio_text_free_nucleus(trexio_text_t* file) {
     nucleus->file = NULL;
   }
 
+  if (nucleus->dims_coord != NULL) {
+    free (nucleus->dims_coord);
+    nucleus->dims_coord = NULL;
+  }
+
   if (nucleus->coord != NULL) {
     free (nucleus->coord);
     nucleus->coord = NULL;
   }
-  
+ 
+  if (nucleus->dims_charge != NULL) {
+    free (nucleus->dims_charge);
+    nucleus->dims_charge = NULL;
+  }
+ 
   if (nucleus->charge != NULL) {
     free (nucleus->charge);
     nucleus->charge = NULL;
@@ -289,7 +346,7 @@ trexio_exit_code trexio_text_write_nucleus_num(const trexio_t* file, const uint6
   return TREXIO_SUCCESS;
 }
 
-trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint64_t dim_coord) {
+trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint32_t rank, const uint64_t* dims) {
 
   if (file  == NULL) return TREXIO_INVALID_ARG_1;
   if (coord == NULL) return TREXIO_INVALID_ARG_2;
@@ -297,9 +354,15 @@ trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* co
   nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
   if (nucleus == NULL) return TREXIO_FAILURE;
 
-  if (dim_coord != nucleus->dim_coord) return TREXIO_INVALID_ARG_3;
+  if (rank != nucleus->rank_coord) return TREXIO_INVALID_ARG_3;
   
-  for (uint64_t i=0 ; i<dim_coord ; i++) {
+  uint64_t dim_size = 1;
+  for (uint i=0; i<rank; i++){
+    if (dims[i] != nucleus->dims_coord[i]) return TREXIO_INVALID_ARG_4;
+    dim_size *= dims[i];
+  }
+
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     coord[i] = nucleus->coord[i];
   }
 
@@ -307,7 +370,7 @@ trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* co
 }
 
  
-trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint64_t dim_coord) {
+trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint32_t rank, const uint64_t* dims) {
   if (file  == NULL)  return TREXIO_INVALID_ARG_1;
   if (coord == NULL)  return TREXIO_INVALID_ARG_2;
 
@@ -321,10 +384,23 @@ trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const dou
     nucleus->coord = NULL;
   }
 
-  nucleus->dim_coord = dim_coord;
-  nucleus->coord = (double*) calloc(dim_coord, sizeof(double));
+  if (nucleus->dims_coord != NULL) {
+    free(nucleus->dims_coord);
+    nucleus->dims_coord = NULL;
+  }
 
-  for (uint64_t i=0 ; i<dim_coord ; i++) {
+  nucleus->rank_coord = rank;
+  nucleus->dims_coord = (uint64_t*) calloc(rank, sizeof(uint64_t));
+  
+  uint64_t dim_size = 1;
+  for (uint i=0; i<nucleus->rank_coord; i++){
+    nucleus->dims_coord[i] = dims[i];
+    dim_size *= dims[i];
+  }
+
+  nucleus->coord = (double*) calloc(dim_size, sizeof(double));
+
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     nucleus->coord[i] = coord[i];
   }
   
@@ -332,7 +408,7 @@ trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const dou
   return TREXIO_SUCCESS;
 }
 
-trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint64_t dim_charge) {
+trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint32_t rank, const uint64_t* dims) {
 
   if (file   == NULL) return TREXIO_INVALID_ARG_1;
   if (charge == NULL) return TREXIO_INVALID_ARG_2;
@@ -340,9 +416,15 @@ trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* c
   nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
   if (nucleus == NULL) return TREXIO_FAILURE;
 
-  if (dim_charge != nucleus->dim_charge) return TREXIO_INVALID_ARG_3;
+  if (rank != nucleus->rank_charge) return TREXIO_INVALID_ARG_3;
   
-  for (uint64_t i=0 ; i<dim_charge ; i++) {
+  uint64_t dim_size = 1;
+  for (uint i=0; i<rank; i++){
+    if (dims[i] != nucleus->dims_charge[i]) return TREXIO_INVALID_ARG_4;
+    dim_size *= dims[i];
+  }
+  
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     charge[i] = nucleus->charge[i];
   }
 
@@ -350,7 +432,7 @@ trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* c
 }
 
  
-trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint64_t dim_charge) {
+trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint32_t rank, const uint64_t* dims) {
   if (file   == NULL)  return TREXIO_INVALID_ARG_1;
   if (charge == NULL)  return TREXIO_INVALID_ARG_2;
 
@@ -364,10 +446,24 @@ trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const do
     nucleus->charge = NULL;
   }
 
-  nucleus->dim_charge = dim_charge;
-  nucleus->charge = (double*) calloc(dim_charge, sizeof(double));
+  if (nucleus->dims_charge != NULL) {
+    free(nucleus->dims_charge);
+    nucleus->dims_charge = NULL;
+  }
 
-  for (uint64_t i=0 ; i<dim_charge ; i++) {
+  nucleus->rank_charge = rank;
+
+  nucleus->dims_charge = (uint64_t*) calloc(rank, sizeof(uint64_t));
+  
+  uint64_t dim_size = 1;
+  for (uint i=0; i<nucleus->rank_charge; i++){
+    nucleus->dims_charge[i] = dims[i];
+    dim_size *= dims[i];
+  }
+
+  nucleus->charge = (double*) calloc(dim_size, sizeof(double));
+
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     nucleus->charge[i] = charge[i];
   }
   
diff --git a/src/trexio_text.h b/src/trexio_text.h
index ea8c1c4..806d180 100644
--- a/src/trexio_text.h
+++ b/src/trexio_text.h
@@ -22,11 +22,13 @@
 
 typedef struct nucleus_s {
   FILE*    file;
-  uint64_t dim_coord;
-  uint64_t dim_charge;
   double*  coord;
   double*  charge;
   uint64_t num;
+  uint64_t* dims_charge;
+  uint64_t* dims_coord;
+  uint32_t rank_charge;
+  uint32_t rank_coord;
   int      to_flush;
 } nucleus_t;
 
@@ -71,11 +73,11 @@ trexio_exit_code trexio_text_free_nucleus(trexio_text_t* file);
 trexio_exit_code trexio_text_read_nucleus_num(const trexio_t* file, uint64_t* num);
 trexio_exit_code trexio_text_write_nucleus_num(const trexio_t* file, const uint64_t num);
 
-trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint64_t dim_coord);
-trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint64_t dim_coord);
+trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint32_t rank, const uint64_t* dims);
+trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint32_t rank, const uint64_t* dims);
 
-trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint64_t dim_charge);
-trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint64_t dim_charge);
+trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint32_t rank, const uint64_t* dims);
+trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint32_t rank, const uint64_t* dims);
 
 rdm_t* trexio_text_read_rdm(trexio_text_t* file);
 
diff --git a/src/trexio_text.org b/src/trexio_text.org
index 310fd88..5104e4c 100644
--- a/src/trexio_text.org
+++ b/src/trexio_text.org
@@ -55,11 +55,13 @@
     #+begin_src c :tangle trexio_text.h
 typedef struct nucleus_s {
   FILE*    file;
-  uint64_t dim_coord;
-  uint64_t dim_charge;
   double*  coord;
   double*  charge;
   uint64_t num;
+  uint64_t* dims_charge;
+  uint64_t* dims_coord;
+  uint32_t rank_charge;
+  uint32_t rank_coord;
   int      to_flush;
 } nucleus_t;
 
@@ -238,7 +240,9 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
   nucleus->file     = NULL;
   nucleus->num      = 0;
   nucleus->coord    = NULL;
+  nucleus->dims_coord = NULL;
   nucleus->charge   = NULL;
+  nucleus->dims_charge = NULL;
   nucleus->to_flush = 0;
 
   /* Try to open the file. If the file does not exist, return */
@@ -264,23 +268,55 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
     int rc;
     rc = fscanf(f, "%s", buffer);
     assert (rc == 1);
-    assert (strcmp(buffer, "dim_charge") == 0);
+    assert (strcmp(buffer, "rank_charge") == 0);
     
-    rc = fscanf(f, "%lu", &(nucleus->dim_charge));
+    rc = fscanf(f, "%u", &(nucleus->rank_charge));
     assert (rc == 1);
+     
+    nucleus->dims_charge = (uint64_t*) calloc(nucleus->rank_charge, sizeof(uint64_t));
+    assert (nucleus->dims_charge != NULL);
+    
+    uint64_t size_charge = 1;
+    for (uint i=0; i<nucleus->rank_charge; i++){
+
+      rc = fscanf(f, "%s", buffer);
+      assert (rc == 1);
+      //assert (strcmp(buffer, "dims_charge") == 0);
+    
+      rc = fscanf(f, "%lu", &(nucleus->dims_charge[i]));
+      assert (rc == 1);
+
+      size_charge *= nucleus->dims_charge[i];
+    }
     
     rc = fscanf(f, "%s", buffer);
     assert (rc == 1);
-    assert (strcmp(buffer, "dim_coord") == 0);
+    assert (strcmp(buffer, "rank_coord") == 0);
     
-    rc = fscanf(f, "%lu", &(nucleus->dim_coord));
+    rc = fscanf(f, "%u", &(nucleus->rank_coord));
     assert (rc == 1);
+     
+    nucleus->dims_coord = (uint64_t*) calloc(nucleus->rank_coord, sizeof(uint64_t));
+    assert (nucleus->dims_coord != NULL);
+    
+    uint64_t size_coord = 1;
+    for (uint i=0; i<nucleus->rank_coord; i++){
+
+      rc = fscanf(f, "%s", buffer);
+      assert (rc == 1);
+      //assert (strcmp(buffer, "dims_coord") == 0);
+    
+      rc = fscanf(f, "%lu", &(nucleus->dims_coord[i]));
+      assert (rc == 1);
+
+      size_coord *= nucleus->dims_coord[i];
+    }
     
     /* Allocate arrays */
-    nucleus->charge = (double*) calloc(nucleus->dim_charge, sizeof(double));
+    nucleus->charge = (double*) calloc(size_charge, sizeof(double));
     assert (nucleus->charge != NULL);
     
-    nucleus->coord = (double*) calloc(nucleus->dim_coord, sizeof(double));
+    nucleus->coord = (double*) calloc(size_coord, sizeof(double));
     assert (nucleus->coord != NULL);
     
     /* Read data */
@@ -295,7 +331,7 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
     assert (rc == 1);
     assert (strcmp(buffer, "charge") == 0);
     
-    for (uint64_t i=0 ; i<nucleus->dim_charge ; i++) {
+    for (uint64_t i=0 ; i<size_charge ; i++) {
       rc = fscanf(f, "%lf", &(nucleus->charge[i]));
       assert (rc == 1);
     }
@@ -304,7 +340,7 @@ nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
     assert (rc == 1);
     assert (strcmp(buffer, "coord") == 0);
     
-    for (uint64_t i=0 ; i<nucleus->dim_coord ; i++) {
+    for (uint64_t i=0 ; i<size_coord ; i++) {
       rc = fscanf(f, "%lf", &(nucleus->coord[i]));
       assert (rc == 1);
     }
@@ -345,19 +381,32 @@ trexio_exit_code trexio_text_flush_nucleus(const trexio_text_t* file) {
   assert (f != NULL);
   rewind(f);
 
-  /* Write the dimensioning variables */
-  fprintf(f, "dim_charge %ld\n", nucleus->dim_charge);
-  fprintf(f, "dim_coord  %ld\n", nucleus->dim_coord );
+  /* Write the dimensioning variables */ 
+  fprintf(f, "rank_charge %d\n", nucleus->rank_charge);
+
+  uint64_t size_charge = 1;
+  for (uint i=0; i<nucleus->rank_charge; i++){
+    fprintf(f, "dims_charge[%d] %ld\n", i, nucleus->dims_charge[i]);
+    size_charge *= nucleus->dims_charge[i];
+  } 
+
+  fprintf(f, "rank_coord %d\n", nucleus->rank_coord);
+
+  uint64_t size_coord = 1;
+  for (uint i=0; i<nucleus->rank_coord; i++){
+    fprintf(f, "dims_coord[%d] %ld\n", i, nucleus->dims_coord[i]);
+    size_coord *= nucleus->dims_coord[i];
+  } 
 
   /* Write arrays */
   fprintf(f, "num %ld\n", nucleus->num);
   fprintf(f, "charge\n");
-  for (uint64_t i=0 ; i<nucleus->dim_charge ; i++) {
+  for (uint64_t i=0 ; i<size_charge ; i++) {
     fprintf(f, "%lf\n", nucleus->charge[i]);
   }
 
   fprintf(f, "coord\n");
-  for (uint64_t i=0 ; i<nucleus->dim_coord ; i++) {
+  for (uint64_t i=0 ; i<size_coord ; i++) {
       fprintf(f, "%lf\n", nucleus->coord[i]);
   }
   fflush(f);
@@ -393,11 +442,21 @@ trexio_exit_code trexio_text_free_nucleus(trexio_text_t* file) {
     nucleus->file = NULL;
   }
 
+  if (nucleus->dims_coord != NULL) {
+    free (nucleus->dims_coord);
+    nucleus->dims_coord = NULL;
+  }
+
   if (nucleus->coord != NULL) {
     free (nucleus->coord);
     nucleus->coord = NULL;
   }
-  
+ 
+  if (nucleus->dims_charge != NULL) {
+    free (nucleus->dims_charge);
+    nucleus->dims_charge = NULL;
+  }
+ 
   if (nucleus->charge != NULL) {
     free (nucleus->charge);
     nucleus->charge = NULL;
@@ -452,12 +511,12 @@ trexio_exit_code trexio_text_write_nucleus_num(const trexio_t* file, const uint6
      The ~coord~ array is assumed allocated with the appropriate size.
     
     #+begin_src c :tangle trexio_text.h
-trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint64_t dim_coord);
-trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint64_t dim_coord);
+trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint32_t rank, const uint64_t* dims);
+trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint32_t rank, const uint64_t* dims);
    #+end_src
 
     #+begin_src c :tangle trexio_text.c
-trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint64_t dim_coord) {
+trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint32_t rank, const uint64_t* dims) {
 
   if (file  == NULL) return TREXIO_INVALID_ARG_1;
   if (coord == NULL) return TREXIO_INVALID_ARG_2;
@@ -465,9 +524,15 @@ trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* co
   nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
   if (nucleus == NULL) return TREXIO_FAILURE;
 
-  if (dim_coord != nucleus->dim_coord) return TREXIO_INVALID_ARG_3;
+  if (rank != nucleus->rank_coord) return TREXIO_INVALID_ARG_3;
   
-  for (uint64_t i=0 ; i<dim_coord ; i++) {
+  uint64_t dim_size = 1;
+  for (uint i=0; i<rank; i++){
+    if (dims[i] != nucleus->dims_coord[i]) return TREXIO_INVALID_ARG_4;
+    dim_size *= dims[i];
+  }
+
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     coord[i] = nucleus->coord[i];
   }
 
@@ -475,7 +540,7 @@ trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* co
 }
 
  
-trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint64_t dim_coord) {
+trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint32_t rank, const uint64_t* dims) {
   if (file  == NULL)  return TREXIO_INVALID_ARG_1;
   if (coord == NULL)  return TREXIO_INVALID_ARG_2;
 
@@ -489,10 +554,23 @@ trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const dou
     nucleus->coord = NULL;
   }
 
-  nucleus->dim_coord = dim_coord;
-  nucleus->coord = (double*) calloc(dim_coord, sizeof(double));
+  if (nucleus->dims_coord != NULL) {
+    free(nucleus->dims_coord);
+    nucleus->dims_coord = NULL;
+  }
 
-  for (uint64_t i=0 ; i<dim_coord ; i++) {
+  nucleus->rank_coord = rank;
+  nucleus->dims_coord = (uint64_t*) calloc(rank, sizeof(uint64_t));
+  
+  uint64_t dim_size = 1;
+  for (uint i=0; i<nucleus->rank_coord; i++){
+    nucleus->dims_coord[i] = dims[i];
+    dim_size *= dims[i];
+  }
+
+  nucleus->coord = (double*) calloc(dim_size, sizeof(double));
+
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     nucleus->coord[i] = coord[i];
   }
   
@@ -505,12 +583,12 @@ trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const dou
      The ~charge~ array is assumed allocated with the appropriate size.
     
     #+begin_src c :tangle trexio_text.h
-trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint64_t dim_charge);
-trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint64_t dim_charge);
+trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint32_t rank, const uint64_t* dims);
+trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint32_t rank, const uint64_t* dims);
    #+end_src
 
     #+begin_src c :tangle trexio_text.c
-trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint64_t dim_charge) {
+trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint32_t rank, const uint64_t* dims) {
 
   if (file   == NULL) return TREXIO_INVALID_ARG_1;
   if (charge == NULL) return TREXIO_INVALID_ARG_2;
@@ -518,9 +596,15 @@ trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* c
   nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
   if (nucleus == NULL) return TREXIO_FAILURE;
 
-  if (dim_charge != nucleus->dim_charge) return TREXIO_INVALID_ARG_3;
+  if (rank != nucleus->rank_charge) return TREXIO_INVALID_ARG_3;
   
-  for (uint64_t i=0 ; i<dim_charge ; i++) {
+  uint64_t dim_size = 1;
+  for (uint i=0; i<rank; i++){
+    if (dims[i] != nucleus->dims_charge[i]) return TREXIO_INVALID_ARG_4;
+    dim_size *= dims[i];
+  }
+  
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     charge[i] = nucleus->charge[i];
   }
 
@@ -528,7 +612,7 @@ trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* c
 }
 
  
-trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint64_t dim_charge) {
+trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint32_t rank, const uint64_t* dims) {
   if (file   == NULL)  return TREXIO_INVALID_ARG_1;
   if (charge == NULL)  return TREXIO_INVALID_ARG_2;
 
@@ -542,10 +626,24 @@ trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const do
     nucleus->charge = NULL;
   }
 
-  nucleus->dim_charge = dim_charge;
-  nucleus->charge = (double*) calloc(dim_charge, sizeof(double));
+  if (nucleus->dims_charge != NULL) {
+    free(nucleus->dims_charge);
+    nucleus->dims_charge = NULL;
+  }
 
-  for (uint64_t i=0 ; i<dim_charge ; i++) {
+  nucleus->rank_charge = rank;
+
+  nucleus->dims_charge = (uint64_t*) calloc(rank, sizeof(uint64_t));
+  
+  uint64_t dim_size = 1;
+  for (uint i=0; i<nucleus->rank_charge; i++){
+    nucleus->dims_charge[i] = dims[i];
+    dim_size *= dims[i];
+  }
+
+  nucleus->charge = (double*) calloc(dim_size, sizeof(double));
+
+  for (uint64_t i=0 ; i<dim_size ; i++) {
     nucleus->charge[i] = charge[i];
   }