Gibbs Workflow -- Phonopy QHA refactor error
The phonopy QHA code was refactored in July 2018 and the variable "_max_t_index" no longer exists. It is currently used here: 

https://github.com/hackingmaterials/atomate/blob/a2cfee5c7cad28e43b2756a4168959a92f4494dc/atomate/vasp/analysis/phonopy.py#L39-L41

This needs to be updated for the current version of phonopy to be used with the Gibbs workflow (should be able to use _len instead).

diff --git a/atomate/vasp/analysis/phonopy.py b/atomate/vasp/analysis/phonopy.py
index ca8cd05a..ed1535f2 100644
--- a/atomate/vasp/analysis/phonopy.py
+++ b/atomate/vasp/analysis/phonopy.py
@@ -53,7 +53,7 @@ def get_phonopy_gibbs(
     )
 
     # gibbs free energy and temperature
-    max_t_index = phonopy_qha._qha._max_t_index
+    max_t_index = phonopy_qha._qha._len
     G = phonopy_qha.get_gibbs_temperature()[:max_t_index]
     T = phonopy_qha._qha._temperatures[:max_t_index]
     return G, T
@@ -178,7 +178,7 @@ def get_phonopy_thermal_expansion(
     )
 
     # thermal expansion coefficient and temperature
-    max_t_index = phonopy_qha._qha._max_t_index
-    alpha = phonopy_qha.get_thermal_expansion()[:max_t_index]
+    max_t_index = phonopy_qha._qha._len
+    alpha = phonopy_qha.get_thermal_expansion()[: max_t_index]
     T = phonopy_qha._qha._temperatures[:max_t_index]
     return alpha, T
diff --git a/requirements.txt b/requirements.txt
index 8d2763d9..fba77727 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 custodian==2022.1.17
 FireWorks==1.9.7
-maggma==0.39.0
+maggma==0.44.0
 monty==2021.6.10
 networkx==2.5.1
 numpy
diff --git a/setup.py b/setup.py
index ce6c78c2..a13e1462 100644
--- a/setup.py
+++ b/setup.py
@@ -25,7 +25,7 @@ if __name__ == "__main__":
         install_requires=[
             "custodian>=2019.8.24",
             "FireWorks>=1.4.0",
-            "maggma>=0.39.0",
+            "maggma>=0.44.0",
             "monty>=2.0.6",
             "networkx",
             "numpy",
['setup.py', 'atomate/vasp/analysis/phonopy.py', 'requirements.txt']