From 340c75b6670884d45f97e353899da7a2336eb17a Mon Sep 17 00:00:00 2001
From: Kipton Barros <kbarros@gmail.com>
Date: Tue, 18 Jun 2024 15:34:33 -0600
Subject: [PATCH] Informative error message regarding zero-spin (#278)

---
 src/System/SpinInfo.jl | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/System/SpinInfo.jl b/src/System/SpinInfo.jl
index c7a84b892..d6663fa39 100644
--- a/src/System/SpinInfo.jl
+++ b/src/System/SpinInfo.jl
@@ -12,9 +12,8 @@ struct SpinInfo
     g      :: Mat3    # Spin g-tensor
 
     function SpinInfo(atom::Int; S, g)
-        if !isinteger(2S)
-            error("Spin $S for atom $atom is not a multiple of 1/2")
-        end
+        S > 0 || error("Spin S must be positive. Use `subcrystal` to discard non-magnetic ions.")
+        isinteger(2S) || error("Spin S must be an exact multiple of 1/2")
         g = typeof(g) <: Number ? Mat3(I*g) : Mat3(g)
         new(atom, S, g)
     end