diff --git a/examples/README b/examples/README
index a0f27e2c05..996176c548 100644
--- a/examples/README
+++ b/examples/README
@@ -112,6 +112,7 @@ tad:      temperature-accelerated dynamics of vacancy diffusion in bulk Si
 threebody: regression test input for a variety of manybody potentials
 vashishta: models using the Vashishta potential
 voronoi:  Voronoi tesselation via compute voronoi/atom command
+wall:     use of reflective walls with different stochastic models
 
 Here is how you might run and visualize one of the sample problems:
 
diff --git a/examples/wall/in.shearflow b/examples/wall/in.shearflow
deleted file mode 100644
index 6e5629cc6e..0000000000
--- a/examples/wall/in.shearflow
+++ /dev/null
@@ -1,50 +0,0 @@
-units		metal
-dimension	3
-boundary	p f p
-
-atom_style		atomic
-neighbor		2.0 bin
-
-
-# create geometry
-
-lattice		sc 10
-region			box block 0 10 0 10 0 10
-create_box		1 box
-create_atoms	1 box
-
-mass		1 39.95
-
-
-
-# LJ potentials
-
-pair_style	lj/cut 8.5
-pair_coeff	* * 0.01 3.4 8.5
-
-
-# initial velocities
-
-
-velocity	all create 300 482748 
-fix			1 all nve
-
-
-# Mirror reflection
-#fix ywalls all wall/reflect ylo EDGE yhi EDGE
-
-# Diffusive reflection, upper wall velocity = 0.1, lower wall fixed
-#fix ywalls all wall/stochastic diffusive 2308 ylo EDGE 300 0 0 0 yhi EDGE 300 0.1 0 0
-
-# Maxwell wall, upper wall velocity = 0.1, lower wall fixed, accommodation coefficient = 0.2 for both walls
-#fix ywalls all wall/stochastic maxwell ylo EDGE 300 0 0 0 0.2 yhi EDGE 300 0 0 0.1 0.2 
-
-# Diffusive reflection, upper wall velocity = 0.1, lower wall fixed, accommodation coefficients = 0.1, 0.2 and 0.3 along directions x,y,z
-fix ywalls all wall/reflect/stochastic 345533 cercignanilampis ylo EDGE 300 0 0 0 0.1 0.2 0.3 yhi EDGE 300 0.1 0 0 0.1 0.2 0.3
-
-# Run
-
-
-thermo			1000
-
-run		1000000
diff --git a/examples/wall/in.wall.ccl b/examples/wall/in.wall.ccl
new file mode 100644
index 0000000000..ba4fb7b827
--- /dev/null
+++ b/examples/wall/in.wall.ccl
@@ -0,0 +1,37 @@
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+create_atoms	1 box
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748 
+fix		1 all nve
+
+# CCL reflection model
+# upper wall velocity = 0.1, lower wall fixed,
+# accommodation coefficients = 0.1, 0.2 and 0.3 along directions x,y,z
+
+fix ywalls all wall/reflect/stochastic ccl 345533 &
+    ylo EDGE 300 0 0 0 0.1 0.2 0.3 yhi EDGE 300 0.1 0 0 0.1 0.2 0.3
+
+# run
+
+thermo		1000
+run		10000
diff --git a/examples/wall/in.wall.diffusive b/examples/wall/in.wall.diffusive
new file mode 100644
index 0000000000..34ccadacac
--- /dev/null
+++ b/examples/wall/in.wall.diffusive
@@ -0,0 +1,36 @@
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+create_atoms	1 box
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748 
+fix		1 all nve
+
+# diffusive reflection
+# upper wall velocity = 0.1, lower wall fixed
+
+fix ywalls all wall/reflect/stochastic diffusive 2308 &
+     ylo EDGE 300 0 0 0 yhi EDGE 300 0.1 0 0
+
+# run
+
+thermo		1000
+run		10000
diff --git a/examples/wall/in.wall.maxwell b/examples/wall/in.wall.maxwell
new file mode 100644
index 0000000000..42d7c98cbe
--- /dev/null
+++ b/examples/wall/in.wall.maxwell
@@ -0,0 +1,37 @@
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+create_atoms	1 box
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748 
+fix		1 all nve
+
+# Maxwellian reflection
+# upper wall velocity = 0.1, lower wall fixed, 
+# accommodation coefficient = 0.2 for both walls
+
+fix ywalls all wall/reflect/stochastic maxwell 29839 &
+     ylo EDGE 300 0 0 0 0.2 yhi EDGE 300 0 0 0.1 0.2 
+
+# run
+
+thermo		1000
+run		10000
diff --git a/examples/wall/in.wall.specular b/examples/wall/in.wall.specular
new file mode 100644
index 0000000000..7fae47e56a
--- /dev/null
+++ b/examples/wall/in.wall.specular
@@ -0,0 +1,34 @@
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+create_atoms	1 box
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748 
+fix		1 all nve
+
+# specular reflection
+
+fix ywalls all wall/reflect ylo EDGE yhi EDGE
+
+# run
+
+thermo		1000
+run		10000
diff --git a/examples/wall/log.9Jan20.wall.ccl.g++.1 b/examples/wall/log.9Jan20.wall.ccl.g++.1
new file mode 100644
index 0000000000..b76b59969a
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.ccl.g++.1
@@ -0,0 +1,94 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 1 by 1 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# CCL reflection model
+# upper wall velocity = 0.1, lower wall fixed,
+# accommodation coefficients = 0.1, 0.2 and 0.3 along directions x,y,z
+
+fix ywalls all wall/reflect/stochastic ccl 345533     ylo EDGE 300 0 0 0 0.1 0.2 0.3 yhi EDGE 300 0.1 0 0 0.1 0.2 0.3
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.137 | 3.137 | 3.137 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    306.83507  -0.80022033            0    38.821664     43.50764 
+    2000    315.15424   -1.9016844            0    38.794461    43.585384 
+    3000    312.36801   -1.8819804            0    38.454377    44.018894 
+    4000    311.67545   -1.9198476            0    38.327078    43.113898 
+    5000    310.81453   -1.9015886            0    38.234167    42.677902 
+    6000    312.35612   -1.9639553            0    38.370867    44.057738 
+    7000    312.24146    -2.042721            0    38.277295    42.858047 
+    8000    313.51516   -2.2080206            0    38.276469    42.739369 
+    9000    313.82536   -2.1370876            0    38.387459    42.315362 
+   10000    310.97164   -1.8717207            0    38.284323    44.847594 
+Loop time of 1.06468 on 1 procs for 10000 steps with 1000 atoms
+
+Performance: 811.511 ns/day, 0.030 hours/ns, 9392.484 timesteps/s
+74.9% CPU use with 1 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 0.12906    | 0.12906    | 0.12906    |   0.0 | 12.12
+Neigh   | 0.8392     | 0.8392     | 0.8392     |   0.0 | 78.82
+Comm    | 0.01259    | 0.01259    | 0.01259    |   0.0 |  1.18
+Output  | 9.9897e-05 | 9.9897e-05 | 9.9897e-05 |   0.0 |  0.01
+Modify  | 0.065229   | 0.065229   | 0.065229   |   0.0 |  6.13
+Other   |            | 0.0185     |            |       |  1.74
+
+Nlocal:    1000 ave 1000 max 1000 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Nghost:    484 ave 484 max 484 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Neighs:    2362 ave 2362 max 2362 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+
+Total # of neighbors = 2362
+Ave neighs/atom = 2.362
+Neighbor list builds = 97
+Dangerous builds = 0
+Total wall time: 0:00:01
diff --git a/examples/wall/log.9Jan20.wall.ccl.g++.4 b/examples/wall/log.9Jan20.wall.ccl.g++.4
new file mode 100644
index 0000000000..109a308651
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.ccl.g++.4
@@ -0,0 +1,94 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 2 by 2 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# CCL reflection model
+# upper wall velocity = 0.1, lower wall fixed,
+# accommodation coefficients = 0.1, 0.2 and 0.3 along directions x,y,z
+
+fix ywalls all wall/reflect/stochastic ccl 345533     ylo EDGE 300 0 0 0 0.1 0.2 0.3 yhi EDGE 300 0.1 0 0 0.1 0.2 0.3
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.085 | 3.09 | 3.096 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    307.61429  -0.85349762            0    38.869007    42.748162 
+    2000    316.84849   -2.1095683            0    38.805357    42.517397 
+    3000    314.15659   -1.9669177            0      38.6004    43.327219 
+    4000    313.37791   -1.8445245            0    38.622242    44.646022 
+    5000    313.79504   -2.1011994            0    38.419432    42.438395 
+    6000    314.34351   -2.1124765            0    38.478979    44.346967 
+    7000    316.05924   -2.2571113            0    38.555899     43.78324 
+    8000    315.02356   -1.8808116            0    38.798459    45.155529 
+    9000    317.88137   -2.1260496            0    38.922253    44.193922 
+   10000    317.81667   -2.1475718            0    38.892376    43.988987 
+Loop time of 0.373009 on 4 procs for 10000 steps with 1000 atoms
+
+Performance: 2316.298 ns/day, 0.010 hours/ns, 26809.007 timesteps/s
+98.6% CPU use with 4 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 0.043001   | 0.060502   | 0.082004   |   6.7 | 16.22
+Neigh   | 0.0089996  | 0.0097498  | 0.011001   |   0.8 |  2.61
+Comm    | 0.151      | 0.17826    | 0.19801    |   4.8 | 47.79
+Output  | 0          | 0          | 0          |   0.0 |  0.00
+Modify  | 0.066      | 0.076501   | 0.087001   |   2.9 | 20.51
+Other   |            | 0.048      |            |       | 12.87
+
+Nlocal:    250 ave 286 max 222 min
+Histogram: 1 1 0 0 0 0 1 0 0 1
+Nghost:    270.5 ave 300 max 242 min
+Histogram: 2 0 0 0 0 0 0 0 0 2
+Neighs:    582.5 ave 742 max 424 min
+Histogram: 1 1 0 0 0 0 0 0 1 1
+
+Total # of neighbors = 2330
+Ave neighs/atom = 2.33
+Neighbor list builds = 88
+Dangerous builds = 0
+Total wall time: 0:00:00
diff --git a/examples/wall/log.9Jan20.wall.diffusive.g++.1 b/examples/wall/log.9Jan20.wall.diffusive.g++.1
new file mode 100644
index 0000000000..ca51670777
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.diffusive.g++.1
@@ -0,0 +1,93 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 1 by 1 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# diffusive reflection
+# upper wall velocity = 0.1, lower wall fixed
+
+fix ywalls all wall/reflect/stochastic diffusive 2308      ylo EDGE 300 0 0 0 yhi EDGE 300 0.1 0 0
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.137 | 3.137 | 3.137 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    312.67753  -0.87571164            0    39.500614    43.641187 
+    2000    320.10672   -1.8866145            0     39.44905    44.817235 
+    3000    317.64782    -1.760419            0    39.257725    46.481585 
+    4000    320.69015   -2.0183637            0    39.392639    44.958979 
+    5000    319.94001   -2.0405034            0    39.273633    42.918123 
+    6000    322.34085   -2.0667328            0    39.557427    45.352614 
+    7000    320.30901    -1.922786            0    39.438999    44.189986 
+    8000    322.25492   -1.9643206            0    39.648742    46.633235 
+    9000    326.28632   -2.0989926            0    40.034649    46.114074 
+   10000    325.68184   -2.1242578            0    39.931326    45.875723 
+Loop time of 0.915023 on 1 procs for 10000 steps with 1000 atoms
+
+Performance: 944.239 ns/day, 0.025 hours/ns, 10928.689 timesteps/s
+50.3% CPU use with 1 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 0.055415   | 0.055415   | 0.055415   |   0.0 |  6.06
+Neigh   | 0.002049   | 0.002049   | 0.002049   |   0.0 |  0.22
+Comm    | 0.0018332  | 0.0018332  | 0.0018332  |   0.0 |  0.20
+Output  | 0          | 0          | 0          |   0.0 |  0.00
+Modify  | 0.85254    | 0.85254    | 0.85254    |   0.0 | 93.17
+Other   |            | 0.003183   |            |       |  0.35
+
+Nlocal:    1000 ave 1000 max 1000 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Nghost:    477 ave 477 max 477 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Neighs:    2325 ave 2325 max 2325 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+
+Total # of neighbors = 2325
+Ave neighs/atom = 2.325
+Neighbor list builds = 97
+Dangerous builds = 0
+Total wall time: 0:00:00
diff --git a/examples/wall/log.9Jan20.wall.diffusive.g++.4 b/examples/wall/log.9Jan20.wall.diffusive.g++.4
new file mode 100644
index 0000000000..76d953b749
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.diffusive.g++.4
@@ -0,0 +1,93 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 2 by 2 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# diffusive reflection
+# upper wall velocity = 0.1, lower wall fixed
+
+fix ywalls all wall/reflect/stochastic diffusive 2308      ylo EDGE 300 0 0 0 yhi EDGE 300 0.1 0 0
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.085 | 3.09 | 3.096 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    310.89471  -0.79880791            0    39.347301    43.751589 
+    2000    320.50481   -2.0317993            0     39.35527    43.068073 
+    3000    318.27899   -2.0007056            0    39.098941    44.164018 
+    4000    317.36789   -1.7177074            0    39.264288    46.423062 
+    5000    320.35583   -2.1568752            0    39.210956    43.576324 
+    6000    320.84464   -2.0723583            0    39.358594     45.13774 
+    7000    322.44996   -2.0841776            0    39.554071    45.974409 
+    8000    318.71892   -1.8599126            0    39.296544    45.737848 
+    9000    317.51275   -1.9303928            0     39.07031    45.138145 
+   10000    318.85556   -2.0522739            0    39.121827    44.160918 
+Loop time of 0.367009 on 4 procs for 10000 steps with 1000 atoms
+
+Performance: 2354.165 ns/day, 0.010 hours/ns, 27247.276 timesteps/s
+97.4% CPU use with 4 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 0.054003   | 0.071752   | 0.097001   |   6.1 | 19.55
+Neigh   | 0.012      | 0.01275    | 0.014      |   0.7 |  3.47
+Comm    | 0.14101    | 0.17301    | 0.198      |   5.3 | 47.14
+Output  | 0.007      | 0.007      | 0.007      |   0.0 |  1.91
+Modify  | 0.045      | 0.060251   | 0.076001   |   5.3 | 16.42
+Other   |            | 0.04225    |            |       | 11.51
+
+Nlocal:    250 ave 278 max 220 min
+Histogram: 1 0 1 0 0 0 0 0 1 1
+Nghost:    270.25 ave 291 max 246 min
+Histogram: 1 0 0 0 1 0 0 1 0 1
+Neighs:    578.25 ave 719 max 389 min
+Histogram: 1 0 0 1 0 0 0 0 0 2
+
+Total # of neighbors = 2313
+Ave neighs/atom = 2.313
+Neighbor list builds = 96
+Dangerous builds = 0
+Total wall time: 0:00:00
diff --git a/examples/wall/log.9Jan20.wall.maxwell.g++.1 b/examples/wall/log.9Jan20.wall.maxwell.g++.1
new file mode 100644
index 0000000000..9467e2645e
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.maxwell.g++.1
@@ -0,0 +1,94 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 1 by 1 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# Maxwellian reflection
+# upper wall velocity = 0.1, lower wall fixed,
+# accommodation coefficient = 0.2 for both walls
+
+fix ywalls all wall/reflect/stochastic maxwell 29839      ylo EDGE 300 0 0 0 0.2 yhi EDGE 300 0 0 0.1 0.2
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.137 | 3.137 | 3.137 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    305.84027  -0.81554574            0    38.677879    43.038024 
+    2000    313.63839   -1.8725314            0    38.627871    43.582384 
+    3000    314.36459   -1.8810929            0    38.713084    44.238028 
+    4000    313.62061   -1.8781065            0        38.62     44.16173 
+    5000    314.62707   -2.0017812            0    38.626291    43.314646 
+    6000    316.56502   -2.0984304            0     38.77989     44.63432 
+    7000    316.76017   -2.1273978            0    38.776123    43.255178 
+    8000    317.92744   -2.2609826            0     38.79327    44.492912 
+    9000    317.48386   -2.1531603            0    38.843812    41.927957 
+   10000    316.18654   -2.0295818            0    38.799865     43.73621 
+Loop time of 1.15703 on 1 procs for 10000 steps with 1000 atoms
+
+Performance: 746.740 ns/day, 0.032 hours/ns, 8642.825 timesteps/s
+24.6% CPU use with 1 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 1.0516     | 1.0516     | 1.0516     |   0.0 | 90.89
+Neigh   | 0.015567   | 0.015567   | 0.015567   |   0.0 |  1.35
+Comm    | 0.01       | 0.01       | 0.01       |   0.0 |  0.86
+Output  | 0          | 0          | 0          |   0.0 |  0.00
+Modify  | 0.070344   | 0.070344   | 0.070344   |   0.0 |  6.08
+Other   |            | 0.009534   |            |       |  0.82
+
+Nlocal:    1000 ave 1000 max 1000 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Nghost:    475 ave 475 max 475 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Neighs:    2334 ave 2334 max 2334 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+
+Total # of neighbors = 2334
+Ave neighs/atom = 2.334
+Neighbor list builds = 90
+Dangerous builds = 0
+Total wall time: 0:00:01
diff --git a/examples/wall/log.9Jan20.wall.maxwell.g++.4 b/examples/wall/log.9Jan20.wall.maxwell.g++.4
new file mode 100644
index 0000000000..31f81e0182
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.maxwell.g++.4
@@ -0,0 +1,94 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 2 by 2 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0.000599861 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# Maxwellian reflection
+# upper wall velocity = 0.1, lower wall fixed,
+# accommodation coefficient = 0.2 for both walls
+
+fix ywalls all wall/reflect/stochastic maxwell 29839      ylo EDGE 300 0 0 0 0.2 yhi EDGE 300 0 0 0.1 0.2
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.085 | 3.09 | 3.096 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    306.84606  -0.81991676            0    38.803387    42.677043 
+    2000    315.55292   -1.9938298            0    38.753798    43.826963 
+    3000    315.05535   -1.9899076            0    38.693469    43.699674 
+    4000    313.78121   -1.8410878            0    38.677757    44.457758 
+    5000     317.0712   -2.1014946            0     38.84219    43.200259 
+    6000    316.56544   -2.0144551            0    38.863921    44.622296 
+    7000    318.00823   -2.0601205            0    39.004564     45.31096 
+    8000    316.36755   -1.8389853            0    39.013836     45.50011 
+    9000       318.31   -2.1029696            0    39.000683    44.238038 
+   10000    317.06931   -2.0706174            0    38.872823    44.009842 
+Loop time of 0.372642 on 4 procs for 10000 steps with 1000 atoms
+
+Performance: 2318.579 ns/day, 0.010 hours/ns, 26835.401 timesteps/s
+94.8% CPU use with 4 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 0.060702   | 0.074426   | 0.103      |   6.3 | 19.97
+Neigh   | 0.006001   | 0.0081906  | 0.010001   |   1.6 |  2.20
+Comm    | 0.13       | 0.18175    | 0.21098    |   7.2 | 48.77
+Output  | 0          | 6.2346e-05 | 0.00024939 |   0.0 |  0.02
+Modify  | 0.039276   | 0.066821   | 0.090003   |   7.1 | 17.93
+Other   |            | 0.04139    |            |       | 11.11
+
+Nlocal:    250 ave 278 max 221 min
+Histogram: 1 1 0 0 0 0 0 0 0 2
+Nghost:    286.25 ave 308 max 263 min
+Histogram: 1 1 0 0 0 0 0 0 1 1
+Neighs:    573.5 ave 724 max 413 min
+Histogram: 1 1 0 0 0 0 0 0 1 1
+
+Total # of neighbors = 2294
+Ave neighs/atom = 2.294
+Neighbor list builds = 99
+Dangerous builds = 0
+Total wall time: 0:00:00
diff --git a/examples/wall/log.9Jan20.wall.specular.g++.1 b/examples/wall/log.9Jan20.wall.specular.g++.1
new file mode 100644
index 0000000000..3d85cb02e7
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.specular.g++.1
@@ -0,0 +1,92 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 1 by 1 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# specular reflection
+
+fix ywalls all wall/reflect ylo EDGE yhi EDGE
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.137 | 3.137 | 3.137 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    305.24846  -0.81252388            0    38.604479    42.984882 
+    2000    313.42563   -1.9181413            0    38.554788    43.314782 
+    3000      312.765   -1.8445772            0    38.543044    44.006858 
+    4000    312.70958   -1.8420045            0     38.53846    44.808265 
+    5000     313.4634   -1.9373681            0    38.540438     43.27283 
+    6000    314.19203   -2.0319378            0    38.539957    44.403177 
+    7000    314.51643   -2.0700345            0    38.543751    42.566368 
+    8000    314.67639   -2.0991652            0    38.535275     44.02504 
+    9000    315.17416   -2.1591689            0     38.53955    43.421838 
+   10000    314.20849   -2.0315185            0    38.542502    43.522426 
+Loop time of 1.08403 on 1 procs for 10000 steps with 1000 atoms
+
+Performance: 797.028 ns/day, 0.030 hours/ns, 9224.862 timesteps/s
+56.0% CPU use with 1 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 0.96636    | 0.96636    | 0.96636    |   0.0 | 89.15
+Neigh   | 0.0087926  | 0.0087926  | 0.0087926  |   0.0 |  0.81
+Comm    | 0.022686   | 0.022686   | 0.022686   |   0.0 |  2.09
+Output  | 0          | 0          | 0          |   0.0 |  0.00
+Modify  | 0.071106   | 0.071106   | 0.071106   |   0.0 |  6.56
+Other   |            | 0.01508    |            |       |  1.39
+
+Nlocal:    1000 ave 1000 max 1000 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Nghost:    480 ave 480 max 480 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+Neighs:    2304 ave 2304 max 2304 min
+Histogram: 1 0 0 0 0 0 0 0 0 0
+
+Total # of neighbors = 2304
+Ave neighs/atom = 2.304
+Neighbor list builds = 87
+Dangerous builds = 0
+Total wall time: 0:00:01
diff --git a/examples/wall/log.9Jan20.wall.specular.g++.4 b/examples/wall/log.9Jan20.wall.specular.g++.4
new file mode 100644
index 0000000000..9c957f80ed
--- /dev/null
+++ b/examples/wall/log.9Jan20.wall.specular.g++.4
@@ -0,0 +1,92 @@
+LAMMPS (09 Jan 2020)
+units		metal
+dimension	3
+boundary	p f p
+
+atom_style	atomic
+neighbor	2.0 bin
+
+# create geometry
+
+lattice		sc 10
+Lattice spacing in x,y,z = 10 10 10
+region		box block 0 10 0 10 0 10
+create_box	1 box
+Created orthogonal box = (0 0 0) to (100 100 100)
+  1 by 2 by 2 MPI processor grid
+create_atoms	1 box
+Created 1000 atoms
+  create_atoms CPU = 0 secs
+
+mass		1 39.95
+
+# LJ potentials
+
+pair_style	lj/cut 8.5
+pair_coeff	* * 0.01 3.4 8.5
+
+# initial velocities
+
+velocity	all create 300 482748
+fix		1 all nve
+
+# specular reflection
+
+fix ywalls all wall/reflect ylo EDGE yhi EDGE
+
+# run
+
+thermo		1000
+run		10000
+Neighbor list info ...
+  update every 1 steps, delay 10 steps, check yes
+  max neighbors/atom: 2000, page size: 100000
+  master list distance cutoff = 10.5
+  ghost atom cutoff = 10.5
+  binsize = 5.25, bins = 20 20 20
+  1 neighbor lists, perpetual/occasional/extra = 1 0 0
+  (1) pair lj/cut, perpetual
+      attributes: half, newton on
+      pair build: half/bin/atomonly/newton
+      stencil: half/bin/3d/newton
+      bin: standard
+Per MPI rank memory allocation (min/avg/max) = 3.085 | 3.09 | 3.096 Mbytes
+Step Temp E_pair E_mol TotEng Press 
+       0          300            0            0    38.739265    41.378094 
+    1000    305.18674  -0.80847964            0    38.600554    42.877223 
+    2000    313.99246   -1.9948292            0    38.551295    43.475585 
+    3000    313.86673    -1.987971            0    38.541917    43.155182 
+    4000    313.11947   -1.8945644            0     38.53883    44.035201 
+    5000    314.92476   -2.1260059            0    38.540507    42.012978 
+    6000    313.46259     -1.93896            0    38.538742    44.197131 
+    7000    314.97475   -2.1392782            0     38.53369     43.91008 
+    8000    313.88617   -1.9970823            0    38.535317    44.277056 
+    9000     314.1612   -2.0304174            0    38.537496    43.495036 
+   10000     315.4836   -2.2052704            0    38.533406    42.624901 
+Loop time of 0.337861 on 4 procs for 10000 steps with 1000 atoms
+
+Performance: 2557.262 ns/day, 0.009 hours/ns, 29597.934 timesteps/s
+96.8% CPU use with 4 MPI tasks x no OpenMP threads
+
+MPI task timing breakdown:
+Section |  min time  |  avg time  |  max time  |%varavg| %total
+---------------------------------------------------------------
+Pair    | 0.044001   | 0.059837   | 0.1        |   9.5 | 17.71
+Neigh   | 0.0062642  | 0.0090668  | 0.015001   |   3.7 |  2.68
+Comm    | 0.144      | 0.18421    | 0.21583    |   6.2 | 54.52
+Output  | 0          | 0.0042874  | 0.017      |  11.2 |  1.27
+Modify  | 0.031019   | 0.037255   | 0.045001   |   2.7 | 11.03
+Other   |            | 0.0432     |            |       | 12.79
+
+Nlocal:    250 ave 278 max 220 min
+Histogram: 2 0 0 0 0 0 0 0 0 2
+Nghost:    277.5 ave 302 max 252 min
+Histogram: 1 0 1 0 0 0 0 1 0 1
+Neighs:    568 ave 709 max 391 min
+Histogram: 1 0 1 0 0 0 0 0 0 2
+
+Total # of neighbors = 2272
+Ave neighs/atom = 2.272
+Neighbor list builds = 86
+Dangerous builds = 0
+Total wall time: 0:00:00
diff --git a/src/USER-MISC/fix_wall_reflect_stochastic.cpp b/src/USER-MISC/fix_wall_reflect_stochastic.cpp
index 6221395f1d..dc58580d80 100644
--- a/src/USER-MISC/fix_wall_reflect_stochastic.cpp
+++ b/src/USER-MISC/fix_wall_reflect_stochastic.cpp
@@ -116,7 +116,7 @@ FixWallReflectStochastic(LAMMPS *lmp, int narg, char **arg) :
 
         // DIFFUSIVE = no accomodation coeffs
         // MAXWELL = one for all dimensions
-        // CLL = one for each dimension
+        // CCL = one for each dimension
 
         if (rstyle == CCL)
           wallaccom[nwall][dir]= force->numeric(FLERR,arg[iarg+dir+6]);
diff --git a/src/random_mars.cpp b/src/random_mars.cpp
index 396cc7e9f1..a832b3640f 100644
--- a/src/random_mars.cpp
+++ b/src/random_mars.cpp
@@ -149,7 +149,7 @@ double RanMars::besselexp(double theta, double alpha, double cp)
 {
   double first,v1,v2;
 
-  if (theta < 0.0 || alpha < 0.0 || alpha < 1.0)
+  if (theta < 0.0 || alpha < 0.0 || alpha > 1.0)
     error->all(FLERR,"Invalid Bessel exponential distribution parameters");
 
   v1 = uniform();